Renal Expression of the Brain and Muscle Isoforms of Glycogen Phosphorylase in Different Cell Types
Kidney contains glycogen. Glycogen is degraded by glycogen phosphorylase (GP). This enzyme comes in three isoforms, one of which, the brain isozyme (GP BB), is known to occur in kidney. Its pattern of distribution in rat kidney was studied in comparison to that of the muscle isoform (GP MM) with the aim to see if for GP BB and GP MM there were functional similarities in brain and kidney. In immunoblotting and quantitative reverse transcriptase polymerase chain reaction (RT-PCR) experiments, both isozymes and their respective mRNAs were found in kidney homogenates. GP BB was immunocytochemically detected in collecting ducts which were identified by the marker protein aquaporin-2. GP MM was localized exclusively in interstitial cells of cortex and outer medulla. These cells were identified as fibroblasts by their expression of 5′-ectonucleotidase (cortex) or by their morphology (outer medulla). The physiological role of both isozymes is discussed in respect to local demands of energy and of proteoglycan building blocks.
KeywordsGlycogen phosphorylase Brain isozyme Muscle isozyme Rat kidney Collecting duct Fibroblast
We wish to gratefully acknowledge Dr. Brigitte Pfeiffer-Guglielmi’s exploratory experiments that stimulated the initiation of the present study. Thanks are also due to Professor Brigitte Kaissling and Dr. Hubert Loewenheim for their generous gifts of antibodies and to Barbara Birk for technical advice.
- 13.Takashi M, Koshikawa T, Kurobe et al (1989) Elevated concentrations of brain-type glycogen phosphorylase in renal cell carcinoma. Jpn J Cancer Res 80:975–980Google Scholar
- 17.Le Hir M, Hegyi I, Cueni-Loffing D et al (2005) Characterization of renal interstitial fibroblast-specific protein 1/S100A4-positive cells in healthy and inflamed rodent kidneys. Histochem. Cell Biol 123:335–346Google Scholar
- 34.Schmid H, Mall A, Scholz M et al (1980) Unchanged glycolytic capacity in rat kidney under conditions of stimulated gluconeogenesis. Determination of phosphofructokinase and pyruvate kinase in microdissected nephron segments of fasted and acidotic animals. Hoppe-Seyler’s Z Physiol Chem 361:819–827PubMedGoogle Scholar
- 37.Schmid H (1984) Microphotometric succinate dehydrogenase histochemistry in human nephron. Bas Appl Histochem 28:221–231Google Scholar
- 38.Shang J, Lehrman MA (2004) Activation of glycogen phosphorylase with 5–aminoimidazole-4-carboxamide riboside (AICAR). Assessment of glycogen as a precursor of mannosyl residues in glycoconjugates. J Biol Chem 26:12076–12080Google Scholar
- 41.Chen Y-T (2001) Glycogen storage diseases. In: Scriver CR, Beaudet AL, Sly WS et al (eds) The molecular basis of inherited disease, 8th edn. McGraw-Hill, New York, pp 1521–1551Google Scholar