title: Transglutaminase C in cerebellar granule neurons: regulation and localization of substrate cross-linking.
abstract: Covalent cross-linking of cell surface proteins by the calcium-dependent enzyme transglutaminase C may be implicated in cell-cell interactions and growth regulation. We demonstrate the presence of the enzyme in rat cerebellar cortex during postnatal development. Transglutaminase C was induced in cerebellar granule neurons in culture by retinoic acid, dibutyryl- and 8-bromo-cyclic AMP analogues and by cultivation on a biomatrix substratum. Cyclic AMP analogues stimulated transglutaminase activity in protein synthesis-dependent and -independent phases. The enzyme was distributed at focal adhesion sites on the axon. By calcium-dependent covalent incorporation of the primary amine acceptor substrate, 5-(biotinamido)pentylamine, an increase in the Ca(2+)-dependent cross-linking of at least 11 substrate proteins in the presence of retinoic acid and dibutyryl-cyclic AMP was detected. Of these substrates, a subset was labelled on the surface of living granule neurons. A low-molecular-weight substrate, p18, was tentatively identified as the retinoic acid-inducible neurite-promoting factor, midkine. Transglutaminase-mediated amine incorporation, midkine and isopeptide cross-links were co-localized to axonal adhesion sites. The results provide evidence of transglutaminase C-catalysed protein cross-linking activity in cerebellar granule neurons and its possible implication in cell-substratum interactions.
authors.affiliation: School of Biological Sciences, University of Bristol, UK.
authors.forename: M J
authors.initials: MJ
authors.lastname: Perry
authors.forename: S A
authors.initials: SA
authors.lastname: Mahoney
authors.forename: L W
authors.initials: LW
authors.lastname: Haynes
mesh_terms: D000588:Amines; D000818:Animals; D000831:Animals, Newborn; D001710:Biotin / Q000031:analogs & derivatives; D015153:Blotting, Western; D003994:Bucladesine / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000201:enzymology*; D016207:Cytokines / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D007150:Immunohistochemistry; D000078792:Midkine; D015335:Molecular Probes; D009474:Neurons / Q000201:enzymology*; D051381:Rats; D017208:Rats, Wistar; D011503:Transglutaminases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000588:Amines; D002352:Carrier Proteins; D016207:Cytokines; D015335:Molecular Probes; C076022:5-(biotinamido)pentylamine; D000078792:Midkine; D003994:Bucladesine; D001710:Biotin; D011503:Transglutaminases