Unphosphorylated and tyrosine-phosphorylated forms of a focal adhesion protein, paxillin, are substrates for calpain II in vitro: implications for the possible involvement of calpain II in mitosis-specific degradation of paxillin.
Cell-to-substratum adhesion becomes weakened during mitosis of the cell cycle in fibroblasts. The level of one focal adhesion protein, paxillin, is greatly reduced in mitotic-arrested cells. We show here the possible involvement of calpain II, known to be localized in focal adhesion plaques, in the degradation of paxillin. Paxillin is tyrosine-phosphorylated during interphase of the cell cycle by protein tyrosine kinases (PTK) such as c-Src and Csk, and becomes dephosphorylated during mitosis. Our data, however, indicate that tyrosine phosphorylation of paxillin does not affect the rate of paxillin degradation by calpain in vitro.
Yamaguchi
R
R
Department of Biological Responses, Kyoto University, Japan.
Maki
M
M
Hatanaka
M
M
Sabe
H
H
D016475:3T3 Cells; D000818:Animals; D002154:Calpain / Q000378:metabolism*; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008938:Mitosis; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D014443:Tyrosine / Q000378:metabolism*
D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; C496061:PXN protein, human; D051419:Paxillin; D010750:Phosphoproteins; C496062:Pxn protein, mouse; D014443:Tyrosine; D002154:Calpain