Phosphorylation of laminin-1 by protein kinase C.
Several extracellular proteins have been reported to be phosphorylated. Previous studies of our laboratory indicated that laminin-1 can be phosphorylated by protein kinase A (PKA). Moreover, it has been reported that protein kinase C (PKC), although known to be intracellular, can phosphorylate extracellular proteins in the case of cellular damage and/or platelet activation. In the present study we examined the possibility of laminin-1 serving as a substrate of PKC. Amino acid analysis revealed that laminin-1 is phosphorylated by this enzyme on serine residues. Self assembly, heparin binding, and cell attachment on the phosphorylated molecule were then studied. Phosphorylated laminin-1 showed an increased and more rapid self assembly than the non-phosphorylated molecule. Heparin binding and cell attachment experiments indicated enhanced heparin and cell binding capacity of the phosphorylated molecule in comparison to the non- phosphorylated control. These results indicate that laminin-1 can be phosphorylated by protein kinase C. Furthermore, phosphorylation by protein kinase C seems to alter several properties of the molecule, though, the in vivo significance of this phenomenon remains to be studied.
Koliakos
G
G
Department of Biological Chemistry, Medical School, Aristotle University of Thessaloniki, Greece. koliakos@med.auth.gr
Trachana
V
V
Gaitatzi
M
M
Dimitriadou
A
A
D000818:Animals; D000925:Anticoagulants / Q000378:metabolism; D002458:Cell Fractionation; D002460:Cell Line; D004586:Electrophoresis; D006493:Heparin / Q000378:metabolism; D007797:Laminin / Q000378:metabolism*; D008862:Microsomes, Liver / Q000201:enzymology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011868:Radioisotopes; D051381:Rats
D000925:Anticoagulants; D007797:Laminin; D011868:Radioisotopes; C121346:laminin 1; D006493:Heparin; D011493:Protein Kinase C