Abstract
Hereditary long QT syndrome is a fatal arrhythmia associated with gene mutations in potassium and sodium channels that are expressed in ventricle. By employing heterologous expression and making comparisons to cells expressing wild-type human-ether-a-go-go-related protein (HERG), a potassium channel that contributes to I Kr current in ventricular cardiomyocytes, we demonstrate activation of an elevated endoplasmic reticulum (ER) stress response by the mutant I593R HERG potassium channel implicated in long QT syndrome type 2. I593R HERG is trafficking-impaired and forms Triton-insoluble aggregates. Expression of I593R HERG activates the unfolded protein response pathway and, separately, NF-κB signaling, ATF6, the activating transcription factor of the unfolded protein response pathway, is processed into the active transcription factor in the cells expressing I593R HERG. Consistent with ATF6 activation, the ER chaperones/calcium-binding proteins Grp78, Grp94, and calreticulin are elevated in I593R HERG-expressing cells. Coexpression of I593R HERG with wild-type HERG also results in ER stress pathway activation. By eliciting downstream links in signal transduction pathways associated with ER stress, expression of mutant trafficking impaired ion channels may contribute to disease etiology mechanisms that augment those associated with attenuated ion flux.
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Valen, G., Yan, Z. Q., and Hansson, G. K. (2001) Nuclear factor kappa-B and the heart. J. Am. Coll. Cardiol. 38, 307–14.
Ma, Y. and Hendershot, L. M. (2002) The mammalian endoplasmic reticulum as a sensor for cellular stress. Cell Stress Chaperones 7, 222–229.
Kouroku, Y., Fujita, E., Jimbo, A., et al. (2002) Polyglutamine aggregates stimulate ER stress signals and caspase-12 activation. Hum. Mol. Genet. 11, 1505–1515.
Hampton, R. Y. (2003) IRE1: a role in upregulation of ER degradation. Dev. Cell 4, 144–146.
Paschen, W. (2003) Endoplasmic reticulum: a primary target in various acute disorders and degenerative diseases of the brain. Cell Calcium 34, 365–383.
Kaneko, M. and Nomura, Y. (2003) ER signaling in unfolded protein response. Life Sci. 74, 199–205.
Yoshida, H., Okada, T., Haze, K., et al. (2000) ATF6 activated by proteolysis binds in the presence of NF-Y (CBF) directly to the cis-acting element responsible for the mammalian unfolded protein response. Mol. Cell. Biol. 20, 6755–6767.
Pahl, H. L. and Baeuerle, P. A. (1997) The ER-overload response: activation of NF-kappa B. Trends Biochem. Sci. 22, 63–67.
Caspersen, C., Pedersen, P. S., and Treiman, M. (2000) The sarco/endoplasmic reticulum calcium-ATPase 2b is an endoplasmic reticulum stress-inducible protein. J. Biol. Chem. 275, 22363–22372.
Benson, D. W., MacRae, C. A., Vesely, M. R., et al. (1996) Missense mutation in the pore region of HERG causes familial long QT syndrome. Circulation 93, 1791–1795.
Zhou, Z., Gong, Q., Epstein, M. L., and January, C. T. (1998) HERG channel dysfunction in human long QT syndrome. Intracellular transport and functional defects. J. Biol. Chem. 273, 21061–21066.
Sanguinetti, M. C., Jiang, C., Curran, M. E., and Keating, M. T. (1995) A mechanistic link between an inherited and an acquired cardiac arrhythmia: HERG encodes the IKr potassium channel. Cell 81, 299–307.
Sanguinetti, M. C. (1999) Dysfunction of delayed rectifier potassium channels in an inherited cardiac arrhythmia. Ann. NY Acad. Sci. 868, 406–413.
Tseng, G. N. (2001) I(Kr): the hERG channel. J. Mol. Cell. Cardiol. 33, 835–849.
McDonald, T. V., Yu, Z., Ming, Z., et al. (1997) A minK-HERG complex regulates the cardiac potassium current I(Kr). Nature 388, 289–292.
Merlini, G., Bellotti, V., Andreola, et al. (2001) Protein aggregation. Clin. Chem. Lab. Med. 39, 1065–1075.
Kaufman, R. J. (2002) Orchestrating the unfolded protein response in health and disease. J. Clin. Invest. 110, 1389–1398.
Temussi, P. A., Masino, L., and Pastore, A. (2003) From Alzheimer to Huntington: why is a structural understanding so difficult? EMBO J. 22, 355–361.
Forman, M. S., Lee, V. M., and Trojanowski, J. Q. (2003) “Unfolding” pathways in neurodegenerative disease. Trends Neurosci. 26, 407–410.
Kudo, T., Katayama, T., Imaizumi, K., et al. (2002) The unfolded protein response is involved in the pathology of Alzheimer’s disease. Ann. NY Acad. Sci. 977, 349–355.
Oyadomari, S., Araki, E., and Mori, M. (2002) Endoplasmic reticulum stress-mediated apoptosis in pancreatic beta-cells. Apoptosis 7, 335–345.
Araki, E., Oyadomari, S., and Mori, M. (2003) [Diabetes mellitus and endoplasmic reticulum stress]. Seikagaku 75, 1324–1331.
Mohler, P. J., Schott, J. J., Gramolini, A. O., et al. (2003) Ankyrin-B mutation causes type 4 long-QT cardiac arrhythmia and sudden cardiac death. Nature 421, 634–639.
Marks, A. R. (2003) Arrhythmias of the heart: beyond ion channels. Nat. Med. 9, 263–264.
Tjoelker, L.W., Seyfried, C. E., Eddy, R.L., Jr., et al. (1994) Human, mouse, and rat calnexin cDNA cloning: identification of potential calcium binding motifs and gene localization to human chromosome 5. Biochemistry 33, 3229–3236.
Kagan, A., Yu, Z., Fishman, G. I., and McDonald, T. V. (2000) The dominant negative LQT2 mutation A561V reduces wild-type HERG expression. J. Biol. Chem. 275, 11241–11248.
Sanguinetti, M. C., Curran, M. E., Spector, P. S., and Keating, M. T. (1996) Spectrum of HERG K+-channel dysfunction in an inherited cardiac arrhythmia. Proc. Natl. Acad. Sci. USA 93, 2208–2212.
Nakajima, T., Furukawa, T., Tanaka, T., et al. (1998) Novel mechanism of HERG current suppression in LQT2: shift in voltage dependence of HERG inactivation. Circ. Res. 83, 415–422.
Haze, K., Yoshida, H., Yanagi, H., Yura, T., and Mori, K. (1999) Mammalian transcription factor ATF6 is synthesized as a transmembrane protein and activated by proteolysis in response to endoplasmic reticulum stress. Mol. Biol. Cell 10, 3787–3799.
Steiner, H., Winkler, E., Shearman, M. S., Prywes, R., and Haass, C. (2001) Endoproteolysis of the ER stress transducer ATF6 in the presence of functionally inactive presenilins. Neurobiol. Dis. 8, 717–722.
Harding, H. P., Calfon, M., Urano, F., Novoa, I., and Ron, D. (2002) Transcriptional and translational control in the Mammalian unfolded protein response. Annu. Rev. Cell. Dev. Biol. 18, 575–599.
Shen, J., Chen, X., Hendershot, L., and Prywes, R. (2002) ER stress regulation of ATF6 localization by dissociation of BiP/GRP78 binding and unmasking of Golgi localization signals. Dev. Cell 3, 99–111.
Pahl, H. L. and Baeuerle, P. A. (1996) Activation of NF-kappa B by ER stress requires both Ca2+ and reactive oxygen intermediates as messengers. FEBS Lett. 392, 129–136.
Wang, T., Zhang, X., and Li, J. J. (2002) The role of NF-kappaB in the regulation of cell stress responses. Int. Immunopharmacol. 2, 1509–1520.
Ficker, E., Dennis, A. T., Obejero-Paz, C. A., Castaldo, P., Taglialatela, M., and Brown, A. M. (2000) Retention in the endoplasmic reticulum as a mechanism of dominant-negative current suppression in human long QT syndrome. J. Mol. Cell. Cardiol. 32, 2327–2337.
Ng, D. T., Spear, E. D., and Walter, P. (2000) The unfolded protein response regulates multiple aspects of secretory and membrane protein biogenesis and endoplasmic reticulum quality control. J. Cell. Biol. 150, 77–88.
Friedlander, R., Jarosch, E., Urban, J., Volkwein, C., and Sommer, T. (2000) A regulatory link between ER-associated protein degradation and the unfolded-protein response. Nat. Cell. Biol. 2, 379–384.
Thuerauf, D. J., Hoover, H., Meller, J., et al. (2001) Sarco/endoplasmic reticulum calcium ATPase-2 expression is regulated by ATF6 during the endoplasmic reticulum stress response: intracellular signaling of calcium stress in a cardiac myocyte model system. J. Biol. Chem. 276, 48309–48317.
Hung, J. H., Su, I. J., Lei, H. Y., et al. (2004) Endoplasmic reticulum stress stimulates the expression of cyclooxygenase-2 through activation of NF-kappaB and pp38 mitogen-activated protein kinase. J. Biol. Chem. 279, 46384–46392.
Molkentin, J. D. (2004) Calcineurin-NFAT signaling regulates the cardiac hypertrophic response in coordination with the MAPKs. Cardiovasc. Res. 63, 467–475.
Pond, A. L., Scheve, B. K., Benedict, A. T., et al. (2000) Expression of distinct ERG proteins in rat, mouse, and human heart. Relation to functional I(Kr) channels. J. Biol Chem 275, 5997–6006.
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Keller, S.H., Platoshyn, O. & Yuan, J.X.J. Long QT syndrome-associated I593R mutation in HERG potassium channel activates ER stress pathways. Cell Biochem Biophys 43, 365–377 (2005). https://doi.org/10.1385/CBB:43:3:365
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DOI: https://doi.org/10.1385/CBB:43:3:365