Encyclopedia of Signaling Molecules

2018 Edition
| Editors: Sangdun Choi

HB-EGF (Heparin-Binding EGF-Like Growth Factor)

Reference work entry
DOI: https://doi.org/10.1007/978-3-319-67199-4_127

Synonyms

Historical Background

Since the discovery of epidermal growth factor (EGF) in 1962, a total of seven mammalian ligands that bind the EGF receptor (EGFR/ErbB1) have been identified, including transforming growth factor-α (TGFα), amphiregulin (ARG), betacellulin (BTC), epiregulin (ERG), epigen (EPG), and heparin-binding EGF-like growth factor (HB-EGF) (Harris et al. 2003). Historically, HB-EGF was the fourth growth factor to be identified among EGFR-ligands. Major findings regarding HB-EGF are:
  • Discovery of HB-EGF (Higashiyama et al. 1991)

  • Identification of HB-EGF as the diphtheria toxin receptor (DTR) (Naglich et al. 1992; Iwamoto et al. 1994)

  • Identification of HB-EGF’s major role in EGFR transactivation (Prenzel et al. 1999)

  • Establishment of HB-EGF-null mouse lines (Iwamoto et al. 2003; Jackson et al. 2003)

  • Proof of the physiological significance of HB-EGF shedding control in vivo (Yamazaki et al. 2003)

  • Discovery of the nuclear translocation of HB-EGF-CTF (Nanba et al. 2003)

  • Identification of HB-EGF as a promising target for cancer therapy (Miyamoto et al. 2004)

  • Proof of the physiological significance of the interaction between HB-EGF and HSPGs in vivo (Iwamoto et al. 2010)

HB-EGF and ErbB Family Receptor Tyrosine Kinases

HB-EGF is a heparin-binding member of the EGFR ligands that was initially identified in the conditioned medium of human macrophage-like cells (Higashiyama et al. 1991). HB-EGF directly binds to and activates EGFR and ErbB4. The ErbB family of receptor tyrosine kinases (RTKs) consists of four receptors: EGFR/ErbB1, ErbB2, ErbB3, and ErbB4. The EGF family of growth factors binds to and activates ErbB RTKs, resulting in the formation of homo- and heterodimers, autophosphorylation of specific tyrosine residues within their cytoplasmic domains, and subsequent intracellular signaling. In vertebrates, EGF family members vary in their ability to activate distinct ErbB homo- and heterodimers, which may partly account for the differences in their bioactivities. In the case of HB-EGF, although it binds to and activates EGFR and ErbB4 directly, it can also activate ErbB2 and ErbB3 indirectly by heterodimerization (Harris et al. 2003; Mekada and Iwamoto 2008) (Fig. 1).
HB-EGF (Heparin-Binding EGF-Like Growth Factor), Fig. 1

Binding specificity of members of the EGF ligand family to members of the ErbB receptor family. (a) EGF family ligands are separated into four categories by their specificity of binding to members of the ErbB receptor family. ErbB2 has no ligand. ErbB3 is deficient in kinase activity (X). NRG neuregulin, ECD extracellular domain, ICD intracellular domain, PM plasma membrane. (b) ErbB homo- and heterodimier combinations activated by HB-EGF

Ectodomain Shedding

Like other EGF family members, HB-EGF is synthesized as a type I transmembrane protein (proHB-EGF), composed of a signal peptide, propeptide, heparin-binding, EGF-like, juxtamembrane, transmembrane, and cytoplasmic domains (Fig. 2). ProHB-EGF is biologically active as a juxtacrine growth factor that signals to neighboring cells in a nondiffusible manner; it also functions as the receptor for diphtheria toxin (DTR) (Naglich et al. 1992; Iwamoto et al. 1994; Iwamoto and Mekada 2000). ProHB-EGF is cleaved at its juxtamembrane domain by metalloproteinases, in a process called “ectodomain shedding.” Ectodomain shedding of proHB-EGF yields a soluble ectodomain of HB-EGF (sHB-EGF) and a remnant carboxy (C)-terminal fragment (HB-EGF-CTF) (Fig. 2). sHB-EGF is a potent mitogen and chemoattractant for cells expressing its cognate ErbB receptors (Mekada and Iwamoto 2008). On the other hand, HB-EGF-CTF also functions as a signaling molecule. Subsequent to shedding, HB-EGF-CTF is phosphorylated and translocates into the nucleus, where it binds to and regulates several nuclear factors (Nanba et al. 2003; Higashiyama et al. 2008). Because proHB-EGF, sHB-EGF, and HB-EGF-CTF have distinct biological activities, ectodomain shedding is a critical process for HB-EGF proper function (Iwamoto and Mekada 2000; Higashiyama et al. 2008).
HB-EGF (Heparin-Binding EGF-Like Growth Factor), Fig. 2

Ectodomain shedding of HB-EGF. (a) Structure of proHB-EGF. The domain structure of the primary translation product of proHB-EGF is depicted. Ectodomain shedding cleaves off proHB-EGF in the juxtamembrane domain (a large arrow). Proteolytic cleavage also occurs at N-terminal sites (small arrows). MT1-MMP is involved in this cleavage. PM plasma membrane. (b) Ectodomain shedding converts proHB-EGF to sHB-EGF and HB-EGF-CTF

Shedding of proHB-EGF can be stimulated by various physiological and pharmacological stimuli, including G-protein-coupled receptor (GPCR) ligands and phorbol esters. Cellular stresses caused by inflammatory cytokines, reactive oxygen, and osmotic shock can also induce ectodomain shedding. These shedding stimuli activate several intracellular signaling molecules and result in the proteolytic cleavage of proHB-EGF by several metalloproteinases, including members of the ADAM family (Blobel 2005) (Fig. 3).
HB-EGF (Heparin-Binding EGF-Like Growth Factor), Fig. 3

Molecular pathways regulating HB-EGF ectodomain shedding. (a) GPCRs-Ras-ERK pathway. GPCR-ligands including lysophosphatidic acid (LPA), angiotensin II (Ang II), and endothelin (ET) activate GPCR, resulting in activation of the downstream Ras-ERK pathway, which induces HB-EGF shedding. (b) TPA-PKC pathway. Phorbol esters, including TPA, activate protein kinase C (PKC), which induces HB-EGF shedding. (c) Stress-p38MAPK pathway. Cellular stresses including inflammatory cytokines, reactive oxygen, and osmotic shock activate the p38MAPK pathway, which induces HB-EGF shedding. In all cases, sHB-EGF released by ectodomain shedding activates EGFR and the downstream Ras-ERK pathway, resulting in the formation of a positive feedback loop for promoting cell proliferation and migration

GPCR ligands, including lysophosphatidic acid (LPA), thrombin, angiotensin (ANG)-II, and endothelin, have been shown to stimulate EGFR tyrosine phosphorylation, in a process referred to as transactivation (Ohtsu et al. 2006). Transactivation of EGFR is a general function of GPCR signaling and is critical for the mitogenic activity of many GPCR ligands. Transactivation of EGFR is achieved by ectodomain shedding of EGFR ligands, and HB-EGF is often preferentially shed among the EGFR ligands (Prenzel et al. 1999). Ectodomain shedding of HB-EGF results in EGFR activation and subsequent Ras-ERK activation. In turn, activation of the EGFR-Ras-ERK pathway promotes further shedding of EGFR ligands. EGFR signals also induce the transcription of EGFR ligands, resulting in the repeated activation of ligand shedding and EGFR activation (Fig. 3). Thus, stimuli that induce HB-EGF shedding may trigger multiple positive feedback loops that ensure substantial EGFR activation, which potentially contributes to oncogenesis, cancer progression, and other diseases (Miyamoto et al. 2006; Mekada and Iwamoto 2008).

Dysregulation of HB-EGF shedding appears to be implicated in several diseases, including cardiovascular pathologies (cardiac hypertrophy, atherosclerosis, and pulmonary hypertension), cystic fibrosis, and various cancers. Analysis of knock-in mice, expressing transmembrane domain-truncated HB-EGF (HBΔtm), revealed that dysregulated secretion of sHB-EGF induces hyperplastic tissue abnormalities, indicating that ectodomain shedding of proHB-EGF must be strictly controlled in vivo (Yamazaki et al. 2003; Mekada and Iwamoto 2008).

Modes of Action

Ectodomain shedding of proHB-EGF yields sHB-EGF and HB-EGF-CTF. The conversion of the molecular forms and the heparin-binding activity of HB-EGF suggest several modes of HB-EGF action (Fig. 4):
HB-EGF (Heparin-Binding EGF-Like Growth Factor), Fig. 4

HB-EGF action modes. Paracrine and autocrine by sHB-EGF: sHB-EGF acts diffusively on cells expressing EGFR and/or ErbB4 (paracrine). Alternatively, sHB-EGF acts on HB-EGF-expressing cells that also express EGFR and/or ErbB4 (autocrine). Juxtacrine and DTR function by proHB-EGF: ProHB-EGF acts by signaling to neighboring cells in a nondiffusible manner (juxtacrine). ProHB-EGF also functions as the cellular receptor for DT (DTR), mediating the entry of DT into the cytoplasm. Intracrine by HB-EGF-CTF: Subsequent to shedding, HB-EGF-CTF translocates into the nucleus, where it binds to several nuclear factors and regulates cell proliferation and apoptosis. Matricrine by sHB-EGF or proHB-EGF with HSPG: sHB-EGF interacts with HSPG as a co-receptor. ProHB-EGF also interacts with HSPG, which upregulates proHB-EGF activities

Paracrine and autocrine: Conventionally, it is thought that sHB-EGF diffusively functions in a “paracrine” manner on cells expressing EGFR and/or ErbB4. Alternatively, sHB-EGF functions in an “autocrine” manner on its own cell, which also expresses EGFR and/or ErbB4. Studies of knock-in mice expressing an uncleavable mutant form (HBuc mice) indicated that in vivo the major functions of HB-EGF are mediated by sHB-EGF (Yamazaki et al. 2003; Mekada and Iwamoto 2008).

Juxtacrine and DTR function: ProHB-EGF functions in a “juxtacrine” manner by signaling to neighboring cells in a nondiffusible manner. Although sHB-EGF is known to be a potent mitogen, several lines of evidence from in vitro studies suggest that proHB-EGF has a distinct activity from sHB-EGF (Iwamoto and Mekada 2000). ProHB-EGF also functions as the cellular receptor for DT (DTR), mediating the entry of DT into the cytoplasm (Naglich et al. 1992; Iwamoto et al. 1994). Tetraspanin CD9 associates with proHB-EGF, which dramatically increases proHB-EGF activity as a DTR, by increasing the number of functional DTRs on the cell surface; however, the molecular mechanism underlying this process remains unclear (Iwamoto et al. 1994; Iwamoto and Mekada 2000).

Intracrine: HB-EGF-CTF has been found to be biologically active and functions in an “intracrine” manner (Nanba et al. 2003; Higashiyama et al. 2008). Subsequent to shedding, it is phosphorylated and translocates into the nucleus, where it binds to several nuclear factors including PLZF and Bcl-6, and regulates cell proliferation and apoptosis.

Matricrine: HB-EGF has a high affinity for heparin and heparan sulfate (HS) and functions in a “matricrine” manner. Cell surface HS-proteoglycans (HSPGs) modulate various HB-EGF activities. Although the heparin-binding domain per se is not essential for HB-EGF activity, this domain suppresses the activity of the EGF-like domain and binding of heparin or HS to this domain inhibits this suppressive effect (Mekada and Iwamoto 2008). A study revealed that association of proHB-EGF with HSPGs promotes its localization to sites of cell-cell contact and prevents shedding (Prince et al. 2010). These studies suggested that HSPGs would be important regulators of HB-EGF activity, though the physiological significance was unclear. It has been reported that similarly to the HB-EGF-null and HBuc mice, the knock-in mice that express a mutant HB-EGF, lacking heparin-binding activity (HBΔhb mice), show developmental abnormality in the cardiac valves, indicating that interaction between HB-EGF and HSPGs is essential for the physiological function of HB-EGF in this process (Iwamoto et al. 2010). Moreover, another study revealed that the interaction of HB-EGF with HSPGs is regulated by the processing of the N-terminal portion of HB-EGF by MT1-MMP, a membrane-bound metalloprotease (Koshikawa et al. 2010). Since the discovery of HB-EGF, it has been known that the processing of this portion of HB-EGF occurs in addition to ectodomain shedding (Fig. 2); however, its biological meaning remained unclear. N-terminal processing of HB-EGF by MT1-MMP converts HB-EGF into a heparin-independent growth factor with enhanced mitogenic activity and thereby expression of both proteins co-stimulates tumor cell growth in vitro and in vivo. Thus, this processing might be a regulatory mechanism for the interaction of HB-EGF with HSPGs in HB-EGF-mediated processes.

Physiological Functions in Mice

Studies using HB-EGF-null and the mutant knock-in mice revealed that HB-EGF has critical roles in several physiological processes (summarized in Table 1; Mekada and Iwamoto 2008).
HB-EGF (Heparin-Binding EGF-Like Growth Factor), Table 1

Physiological functions and modes of action of HB-EGF in mice

  

Phenotypes

     

Tissue

Process

KO

UC

ΔHB

HB-EGF expression

Effected region

Effects

Mode of action

Refs.a

Heart muscle

Homeostasis

DCM-like

DCM-like

Normal

Cardiomyocytes

Cardiomyocytes

Survival/contraction

Paracrine

Iwamoto et al. (2003), Yamazaki et al. (2003), Iwamoto et al. (2010)

Heart valves

Development

Enlarged

Enlarged

Enlarged

Endocardial cells

Mesenchymal cells

Inhibition of proliferation

Para/

matricrine

Iwamoto et al. (2003), Yamazaki et al. (2003), Iwamoto et al. (2010)

Skin

Eyelid closure

Delay

Delay

n.d.

Leading edge of migrating epithelial sheet

Migrating epithelial sheet

Promotion of migration

Paracrine

Mine et al. (2005)

Skin

Wound healing

Delay

Delay

n.d.

Leading edge of migrating epithelial sheet

Migrating epithelial sheet

Promotion of migration

Paracrine

Shirakata et al. (2005)

Lung

Alveolization

Thickened alveolar wall

n.d.

Normal

Alveolar cells

Alveolar cells

Inhibition of proliferation

n.d.

Minami et al. (2008), Iwamoto et al. (2010)

Uterus

Implantation

Reduced

n.d.

n.d.

Endometrium

Blastocyst

Promotion of implantation

n.d.

Xie et al. (2007)

KO HB-EGF-null mice, UC Knock-in mice expressing uncleavable mutant HB-EGF, ΔHB Knock-in mice expressing heparin-binding domain-truncated mutant HB-EGF, DCM Dilated cardiomyopathy, n.d. not determined

Heart muscle homeostasis: more than half of HB-EGF null mice died after birth and the survivors developed severe heart failure with grossly enlarged ventricular chambers and decreased contractility, symptoms resembling human dilated cardiomyopathy. This phenotype resembled that of mice conditionally lacking ErbB2. The data indicated that HB-EGF activation of ErbB2 and ErbB4 in cardiomyocytes is essential for normal heart function. The HBuc mice showed an essentially similar phenotype, indicating that sHB-EGF functions by paracrine in this process.

Heart valve development: HB-EGF null mice also developed grossly enlarged cardiac valves. This enlargement is due to the increased proliferation of mesenchymal cells in the cardiac jelly during the later stage of cardiac valve development. This phenotype resembled that displayed by mice lacking EGFR and ADAM17, one of the sheddases for HB-EGF. The HBuc mice also showed an essentially similar phenotype, indicating that sHB-EGF functions in this process. These studies proposed a model for valve development in which sHB-EGF secreted by ADAM17 from endocardial cells activates EGFR in mesenchymal cells, resulting in suppression of cell proliferation. As mentioned above, it has been revealed that HB-EGF must interact with HSPGs to properly function in this process. Interestingly, although HB-EGF-null mice had abnormal heart chambers and lung alveoli, HBΔhb/Δhb mice did not exhibit these defects. Thus, the interaction with HSPGs is essential for HB-EGF function, especially in cardiac valve development.

Skin epidermis: Lack of HB-EGF resulted in a defect in eyelid closure in mouse embryos. Together with studies using HBuc, waved-2 (a hypomorphic EGFR mutant strain), and TGFα null mice, the data indicate that sHB-EGF secreted from the tip of the leading edge of migrating epithelium activates the EGFR and ERK pathways, and that synergy with TGFα is required for the leading edge extension in epithelial sheet migration during eyelid closure. A similar mode of paracrine HB-EGF function in epithelial sheet migration underlies the skin wound healing process.

Lung development: HB-EGF is involved in distal lung development. In HB-EGF null newborns, abnormally thick saccular walls occurred accompanied by a significant increase in cell proliferation during the perinatal stage, indicating that HB-EGF suppresses distal lung cell proliferation. Together with studies using waved-2 and TGFα null mice, these findings indicate that HB-EGF has a suppressive function that contributes to decelerating distal lung cell proliferation synergistically with TGFα, through EGFR, during perinatal distal lung development.

Blastocyst implantation: HB-EGF has been suggested to be involved in the interaction between the blastocyst and the uterus during the implantation process. HB-EGF is expressed in the uterine luminal epithelium at the site of the blastocyst before the attachment reaction. Maternal HB-EGF is critical for implantation. Maternal deficiency of HB-EGF defers on-time implantation, leading to a compromised pregnancy outcome. ARG partially compensates for the loss of HB-EGF in this process.

Implications in Pathophysiology

Several clinical and basic studies have shed light on the roles of induction and shedding of the EGF family of growth factors in pathophysiology. Among EGF family, HB-EGF has been prominently studied regarding these issues (summarized in Table 2; Ohtsu et al. 2006; Miyamoto et al. 2006; Higashiyama et al. 2008).
HB-EGF (Heparin-Binding EGF-Like Growth Factor), Table 2

Effect of dysregulation of shedding and expression on HB-EGF-mediated processes and pathophysiology

Shedding/expression

Experimental model

Abnormality/pathophysiology

Tissue

Shedding inducer

Considered sheddase

Refs.

Decreased shedding

HB-EGF KO and UC mice

DCM-like

Heart

  

Iwamoto et al. (2003), Yamazaki et al. (2003)

  

Valve hypertrophy

Heart

 

ADAM17

Iwamoto et al. (2003), Yamazaki et al. (2003)

  

Eyelid closure defect

Skin

 

ADAM17

Mine et al. (2005)

  

Defect in hyperplasia

Skin

tRA

 

Kimura et al. (2005)

 

HB-EGF KO mice

Wound healing defect

Skin

Wounding

 

Shirakata et al. (2005)

 

HB-EGF, ADAM17 and EGFR KO mice

Valve hypertrophy

Heart

 

ADAM17

Jackson et al. (2003)

Increased shedding

Soluble HB-EGF mutant knock-in mice

Hypertrophy

Skin/heart

  

Yamazaki et al. (2003)

 

Heart hypertrophic mice

Hypertrophy

Heart

GPCR-agonists

ADAM12

Asakura et al. (2002)

 

Cell culture

Atherosclerosis

Artery

GPCR-agonists

ADAM17

Ohtsu et al. (2006)

 

Cell culture

Atherosclerosis

Artery

LRPs

 

Kawakami and Yoshida (2005)

 

Hypertensive rats

Hypertension

Artery

GPCR-agonists

MMP7

Hao et al. (2004)

 

Cell culture

Cystic fibrosis

Lung

S. aureus LTA

ADAM10

Lemjabbar and Basbaum (2002)

 

Cell culture, xenografted nude mice

Ovarian cancer

Ovary

LPA

 

Miyamoto et al. (2004)

Cell culture

Invadopodia

Epithelial cancers

Hypoxia

ADAM12

Diaz et al. (2013)

Cell culture

Angiogenesis

Blood vessel

Hypoxia

 

Svensson et al. (2011),

Zebrafish

Regeneration

Retina

Injury

 

Wan et al. (2012)

Increased expression

RPGN model and HB-EGF KO mice

RPGN

Kidney

  

Bollee et al. (2011)

CCl4/BDL models in HB-EGF CKO mice

Liver injury/fibrosis

Liver

  

Takemura et al. (2013a), Takemura et al. (2013b)

I/R model in HB-EGF CKO mice

Cerebral injury

Brain

  

Oyagi et al. (2011)

Cardiac hypertrophy: HB-EGF shedding by a metalloproteinase ADAM12, followed by EGFR transactivation has been reported to be involved in cardiac hypertrophy. When cardiomyocytes are stimulated by GPCR-agonists, shedding of HB-EGF via ADAM12 activation and subsequent transactivation of EGFR occur. In mice with cardiac hypertrophy, KB-R7785 (a metalloproteinase inhibitor) inhibits the shedding of HB-EGF and attenuates hypertrophic changes.

Atherosclerosis and pulmonary hypertension: Atherogenesis in the arterial wall is characterized by the formation of fibrous lesions and proliferation of neointimal smooth muscle cells (SMCs), and HB-EGF is a potent chemoattractant and mitogen for vascular SMCs. Large amounts of HB-EGF mRNA and proteins are expressed in SMCs and macrophages in human atherosclerotic plaques. EGFR transactivation by sHB-EGF through ANG II-GPCR activation is required for the vascular SMC hypertrophy, and ADAM17 may be involved in this process. Remnant lipoproteins (RLPs) have also been reported as inducers of atherosclerosis, mediated by EGFR transactivation via HB-EGF shedding. Stimulation of GPCR with phenylephrine, which causes EGFR transactivation through MMP7 shedding of HB-EGF, has been suggested to be involved in the development and progression of hypertension. In spontaneously hypertensive rats (SHR), MMP levels are high at all time points. Administration of doxycycline, the only clinically approved MMP inhibitor, reduces systolic blood pressure and attenuates HB-EGF shedding in mesenteric arteries of SHR.

Cystic fibrosis: In the lungs of cystic fibrosis patients, it has been suggested that the pathway, bacterial lipoteichoic acid-GPCR-induced ADAM10 activation followed by HB-EGF shedding, and EGFR transactivation, may contribute to this pathology. Overproduction of mucus is a direct result of the activation of mucin gene expression by gram-positive bacteria. Bacterial lipoteichoic acid activates the platelet-activating factor receptor, which is a GPCR. This results in activation of ADAM10, cleavage of proHB-EGF, and activation of EGFR.

Renal injury: Rapidly progressive glomerulonephritis (RPGN) is a life-threatening clinical syndrome. HB-EGF is induced in proliferating intrinsic glomerular epithelial cells from both mice and humans with RPGN. Induced HB-EGF activates EGFR. In HB-EGF KO mice, EGFR activation is absent and the course of RPGN is improved. Together with studies using EGFR conditional KO (CKO) mice and EGFR inhibitors, the data suggested that targeting HB-EGF-EGFR pathway could be beneficial in treatment of human RPGN.

Liver injury: HB-EGF is experimentally induced in response to several liver injury models, including carbon tetrachloride (CCl4)-injection and bile duct ligation (BDL)-induced fibrotic liver. Liver-specific HB-EGF CKO mice showed enhanced exacerbation of symptoms in both model, suggesting that HB-EGF plays a protective role during those liver injury.

Neural injury: HB-EGF is experimentally induced in a hypoxia condition by focal cerebral ischemia and reperfusion (I/R) injury model. Forebrain-specific HB-EGF CKO mice showed exacerbated injury, suggesting that HB-EGF plays a protective role during the neural injury.

Cancers: Emerging evidence has implicated dysregulation of expression and ectodomain shedding of EGF family growth factors, especially HB-EGF, in the proliferative potential of tumor cells. It has been revealed that HB-EGF is a critical factor for ovarian cancer progression and thus suggested that HB-EGF could be a novel target molecule for therapy of this cancer. Subsequently, CRM197 (a nontoxic mutant DT that neutralizes HB-EGF activity) is undergoing clinical development as an anticancer drug. Tumor progression involves the interaction of cancer cells with the cancer-surrounding stroma. A study using CRM197 and humanized HB-EGF-expressing knock-in mice has revealed that not only HB-EGF in cancer cells but also cancer stroma-derived HB-EGF contributes to tumor growth (Ichise et al. 2010). Consistently, HB-EGF is expressed also in the cancer-surrounding stroma, which is involved in uterine cervical cancer progression (Murata et al. 2011).

Hypoxia in cancer cells: A recent study reported that HB-EGF and its shedding are critical for hypoxia-induced Notch-mediated invadopodia formation in vitro. In several cancer cells, hypoxia increased the levels and activity of the ADAM12 metalloproteinase in a Notch signaling-dependent manner, resulting in increased HB-EGF shedding. Released HB-EGF activated EGFR, which leads to the formation of invadopodia, cellular structures that aid cancer cell invasion. Another recent study also demonstrated that HB-EGF is critically involved in the hypoxia-induced signaling axis that links coagulation activation in cancer cells to activation of endothelial cells that is mediated by PAR (protease-activated receptor)-2, a GPCR.

Retina regeneration in zebrafish: A recent study demonstrated that HB-EGF and its ectodomain shedding play critical roles for Muller glia (MG) dedifferentiation to a cycling population of multipotent progenitors, that is crucial to the retina regeneration in zebrafish. HB-EGF is rapidly induced in MG residing at the injury site, and mediates its effects via an EGFR/MAPK pathway, regulating the expression of regeneration-associated genes. Moreover, HB-EGF acted upstream of Wnt/β-catenin signaling cascade that controls the progenitor proliferation.

Summary

HB-EGF is a member of the EGF family of growth factors, which binds to and activates EGFR and ErbB4. HB-EGF is synthesized first as a transmembrane proHB-EGF. Ectodomain shedding of proHB-EGF yields sHB-EGF and HB-EGF-CTF. Each form of HB-EGF has a distinct biological activity, and functions in several modes of action. Thus, ectodomain shedding is a critical process that must be strictly controlled for HB-EGF to function properly. Dysregulated shedding of HB-EGF causes severe developmental abnormalities in mice and has also been implicated in several pathologies. HSPGs are also important regulators of HB-EGF functions. Interaction with HSPGs is essential for HB-EGF function in mouse cardiac valve development. N-terminal processing of HB-EGF by MT1-MMP is a regulatory step for this interaction. HB-EGF has been implicated in several developmental, physiological, and pathological processes. Although HB-EGF has conventionally been thought of as a growth-promoting factor, especially in pathological processes including cancers, HB-EGF does not function as a growth-promoting factor, but rather as a growth-inhibitory or migration-promoting factor in developmental and physiological processes. Thus, future studies will clarify the mechanism regulating HB-EGF normal function in vivo (not as a growth-promoting factor), which will lead to novel therapeutic approaches for several HB-EGF-mediated pathologies.

References

  1. Asakura M, Kitakaze M, Takashima S, Liao Y, Ishikura F, Yoshinaka T, et al. Cardiac hypertrophy is inhibited by antagonism of ADAM12 processing of HB-EGF: metalloproteinase inhibitors as a new therapy. Nat Med. 2002;8:35–40. doi: 10.1038/nm0102-35.PubMedCrossRefGoogle Scholar
  2. Blobel CP. ADAMs: key components in EGFR signaling and development. Nat Rev Mol Cell Biol. 2005;6:32–43. doi: 10.1038/nrm1548.PubMedCrossRefGoogle Scholar
  3. Bollee G, Flamant M, Schordan S, Fligny C, Rumpel E, Milon M, et al. Epidermal growth factor receptor promotes glomerular injury and renal failure in rapidly progressive crescentic glomerulonephritis. Nat Med. 2011;17:1242–50. doi: 10.1038/nm.2491.PubMedPubMedCentralCrossRefGoogle Scholar
  4. Diaz B, Yuen A, Iizuka S, Higashiyama S, Courneidge SA. Notch increases the shedding of HB-EGF by ADAM12 to potentiate invadopodia formation in hypoxia. J Cell Biol. 2013;201:279–92. doi: 10.1083/jcb.201209151.PubMedPubMedCentralCrossRefGoogle Scholar
  5. Hao L, Du M, Lopez-Campistrous A, Fernandez-Parton C. Agonist-induced activation of matrix metalloproteinase-7 promotes vasoconstriction through the epidermal growth factor-receptor pathway. Circ Res. 2004;94:68–76. doi: 10.1161/01.RES.0000109413.57726.91.PubMedCrossRefGoogle Scholar
  6. Harris RC, Chung E, Coffey RJ. EGF receptor ligands. Exp Cell Res. 2003;284:2–13. doi: 10.1016/S0014-4827(02)00105-2.PubMedCrossRefGoogle Scholar
  7. Higashiyama S, Abraham JA, Miller J, Fiddes JC, Klagsbrun M. A heparin-binding growth factor secreted by macrophage-like cells that is related to EGF. Science. 1991;251:936–9. doi: 10.1126/science.1840698.PubMedCrossRefGoogle Scholar
  8. Higashiyama S, Iwabuki H, Morimoto C, Hieda M, Inoue H, Matsushita N. Membrane-anchored growth factors, the epidermal growth factor family: beyond receptor ligands. Cancer Sci. 2008;99:214–20. doi: 10.1111/j.1349-7006.2007.00676.x.PubMedCrossRefGoogle Scholar
  9. Ichise T, Adachi S, Ohishi M, Ikawa M, Okabe M, Iwamoto R, et al. Humanized gene replacement in mice reveals the contribution of cancer stroma-derived HB-EGF to tumor growth. Cell Struct Funct. 2010;35:3–13. doi: 10.1247/csf.09025.PubMedCrossRefGoogle Scholar
  10. Iwamoto R, Higashiyama S, Mitamura T, Taniguchi N, Klagsbrun M, Mekada E. Heparin-binding EGF-like growth factor, which acts as the diphtheria toxin receptor, forms a complex with membrane protein DRAP27/CD9, which up-regulates functional receptors and diphtheria toxin sensitivity. EMBO J. 1994;13:2322–30.PubMedPubMedCentralGoogle Scholar
  11. Iwamoto R, Mekada E. Heparin-binding EGF-like growth factor: a juxtacrine growth factor. Cytokine Growth Factor Rev. 2000;11:335–44. doi: 10.1016/S1359-6101(00)00013-7.PubMedCrossRefGoogle Scholar
  12. Iwamoto R, Yamazaki S, Asakura M, Takashima S, Hasuwa H, Miyado K, et al. Heparin-binding EGF-like growth factor and ErbB signaling is essential for heart function. Proc Natl Acad Sci USA. 2003;100:3221–6. doi: 10.1073/pnas.0537588100.PubMedPubMedCentralCrossRefGoogle Scholar
  13. Iwamoto R, Mine N, Kawaguchi T, Minami S, Saeki K, Mekada E. HB-EGF function in cardiac valve development requires interaction with heparan sulfate proteoglycans. Development. 2010;137:2205–14. doi: 10.1242/dev.048926.PubMedCrossRefGoogle Scholar
  14. Jackson LF, Qiu TH, Sunnarborg SW, Chang A, Zhang C, Patterson C, et al. Defective valvulogenesis in HB-EGF and TACE-null mice is associated with aberrant BMP signaling. EMBO J. 2003;22:2704–16. doi: 10.1093/emboj/cdg264.PubMedPubMedCentralCrossRefGoogle Scholar
  15. Kawakami A, Yoshida M. Remnant lipoproteins and atherogenesis. J Atheroscler Thromb. 2005;12:73–6. doi: 10.5551/jat.12.73.PubMedCrossRefGoogle Scholar
  16. Kimura R, Iwamoto R, Mekada E. Soluble form of heparin-binding EGF-like growth factor contributes to retinoic acid-induced epidermal hyperplasia. Cell Struct Funct. 2005;30:35–42. doi: 10.1247/csf.30.35.PubMedCrossRefGoogle Scholar
  17. Koshikawa N, Mizushima H, Minegishi T, Iwamoto R, Mekada E, Seiki M. Membrane type 1-matrix metalloproteinase cleaves off the NH2-terminal portion of heparin-binding epidermal growth factor and converts it into a heparin-independent growth factor. Cancer Res. 2010;70:6093–103. doi: 10.1158/0008-5472.CAN-10-0346.PubMedCrossRefGoogle Scholar
  18. Lemjabbar H, Basbaum C. Platelet-activating factor receptor and ADAM10 mediate responses to Staphylococcus aureus in epithelial cells. Nat Med. 2002;8:41–6. doi: 10.1038/nm0102-41.PubMedCrossRefGoogle Scholar
  19. Mekada E, Iwamoto R. HB-EGF. UCSD-Nature Molecule Pages. 2008. doi: 10.1038/mp.a002932.01.Google Scholar
  20. Minami S, Iwamoto R, Mekada E. HB-EGF decelerates cell proliferation synergistically with TGFα in perinatal distal lung development. Dev Dyn. 2008;237:247–58. doi: 10.1002/dvdy.21398.PubMedCrossRefGoogle Scholar
  21. Mine N, Iwamoto R, Mekada E. HB-EGF promotes epithelial cell migration in eyelid development. Development. 2005;132:4317–26. doi: 10.1242/dev.02030.PubMedCrossRefGoogle Scholar
  22. Miyamoto S, Hirata M, Yamazaki A, Kageyama T, Hasuwa H, Mizushima H, et al. Heparin-binding EGF-like growth factor is a promising target for ovarian cancer therapy. Cancer Res. 2004;64:5720–7. doi: 10.1158/0008-5472.CAN-04-0811.PubMedCrossRefGoogle Scholar
  23. Miyamoto S, Yagi H, Yotsumoto F, Kawarabayashi T, Mekada E. Heparin-binding epidermal growth factor-like growth factor as a novel targeting molecule for cancer therapy. Cancer Sci. 2006;97:341–7. doi: 10.1111/j.1349-7006.2006.00188.x.PubMedCrossRefGoogle Scholar
  24. Murata T, Mizushima H, Chinen I, Moribe H, Yagi S, Hoffman RM, et al. HB-EGF and PDGF mediate reciprocal interactions of carcinoma cells with cancer-associated fibroblasts to support progression of uterine cervical cancers. Cancer Res. 2011;71:6632–42. doi: 10.1158/0008-5472.CAN-11-0034.CrossRefGoogle Scholar
  25. Naglich JG, Metherall JE, Russell DW, Eidels L. Expression cloning of a diphtheria toxin receptor: identity with a heparin-binding EGF-like growth factor precursor. Cell. 1992;69:1051–61. doi: 10.1016/0092-8674(92)90623-K.PubMedCrossRefGoogle Scholar
  26. Nanba D, Mammoto A, Hashimoto K, Higashiyama S. Proteolytic release of the carboxy-terminal fragment of proHB-EGF causes nuclear export of PLZF. J Cell Biol. 2003;163:489–502. doi: 10.1083/jcb.200303017.PubMedPubMedCentralCrossRefGoogle Scholar
  27. Ohtsu H, Dempsey PJ, Eguchi S. ADAMs as mediators of EGF receptor transactivation by G protein-coupled receptors. Am J Physiol Cell Physiol. 2006;291:1–10. doi: 10.1152/ajpcell.00620.2005.CrossRefGoogle Scholar
  28. Oyagi A, Morimoto N, Hamanaka J, Ishiguro M, Tsuruma K, Shimazawa M, et al. Forebrain-specific heparin-binding epidermal growth factor-like growth factor knockout mice show exacerbated ischemia and reperfusion injury. Neuroscience. 2011;185:116–24. doi: 10.1016/j.neuroscience.2011.04.034.PubMedCrossRefGoogle Scholar
  29. Prenzel N, Zwick E, Daub H, Leserer M, Abraham R, Wallasch C, et al. EGF receptor transactivation by G-protein-coupled receptors requires metalloproteinase cleavage of proHB-EGF. Nature. 1999;402:884–8. doi: 10.1038/47260.PubMedGoogle Scholar
  30. Prince RN, Schreiter ER, Zou P, Wiley HS, Ting AY, Lee RT, et al. The heparin-binding domain of HB-EGF mediates localization to sites of cell-cell contact and prevents HB-EGF proteolytic release. J Cell Sci. 2010;123:2308–18. doi: 10.1242/jcs.058321.PubMedPubMedCentralCrossRefGoogle Scholar
  31. Shirakata Y, Kimura R, Nanba D, Iwamoto R, Tokumaru S, Morimoto C, et al. Heparin-binding EGF-like growth factor accelerates keratinocyte migration and skin wound healing. J Cell Sci. 2005;118:2363–70. doi: 10.1242/jcs.02346.PubMedCrossRefGoogle Scholar
  32. Svensson KJ, Kucharzewska P, Christianson HC, Skold S, Lofstedt T, Johansson MC, et al. Hypoxia triggers a proangiogenic pathway involving cancer cell microvesicles and PAR-2-mediated heparin-binding EGF signaling in endothelial cells. Proc Natl Acad Sci USA. 2011;108:13147–52. doi: 10.1073/pnas.1104261108.PubMedPubMedCentralCrossRefGoogle Scholar
  33. Takemura T, Yoshida Y, Kiso S, Saji Y, Ezaki H, Hamano M, et al. Conditional knockout of heparin-binding epidermal growth factor-like growth factor in the liver accelerates carbon tetrachloride-induced liver injury in mice. Hepatol Res. 2013a;43:384–93. doi: 10.1111/j.1872-034X.2012.01074.x.PubMedCrossRefGoogle Scholar
  34. Takemura T, Yoshida Y, Kiso S, Kizu T, Furuta K, Ezaki H, et al. Conditional loss of heparin-binding EGF-like growth factor results in enhanced liver fibrosis after bile duct ligation in mice. Biochem Biophys Res Commun. 2013b;437:185–91. doi: 10.1016/j.bbrc.2013.05.097.PubMedCrossRefGoogle Scholar
  35. Wan J, Ramachandran R, Goldman D. HB-EGF is necessary and sufficient for Muller glia dedifferentiation and retina regeneration. Dev Cell. 2012;22:334–47. doi: 10.1016/j.devcel.2011.11.020.PubMedPubMedCentralCrossRefGoogle Scholar
  36. Xie H, Wang H, Tranguch S, Iwamoto R, Mekada E, DeMayo FJ, et al. Maternal heparin-binding-EGF deficiency limits pregnancy success in mice. Proc Natl Acad Sci USA. 2007;104:18315–20. doi: 10.1073/pnas.0707909104.PubMedPubMedCentralCrossRefGoogle Scholar
  37. Yamazaki S, Iwamoto R, Saeki K, Asakura M, Takashima S, Yamazaki A, et al. Mice with defects in HB-EGF ectodomain shedding show severe developmental abnormalities. J Cell Biol. 2003;163:469–75. doi: 10.1083/jcb.200307035.PubMedPubMedCentralCrossRefGoogle Scholar

Copyright information

© Springer International Publishing AG 2018

Authors and Affiliations

  1. 1.Department of Cell Biology, Research Institute for Microbial DiseasesOsaka UniversitySuita, OsakaJapan