p34cdc2-mediated phosphorylation mobilizes microtubule-organizing centers from the apical intermediate filament scaffold in CACO-2 epithelial cells.
We have shown previously that centrosomes and other microtubule-organizing centers (MTOCs) attach to the apical intermediate filament (IF) network in CACO-2 cells. In this cell line, intermediate filaments do not disorganize during mitosis. Therefore, we speculated that the trigger of the G(2)-M boundary may also detach MTOCs from their IF anchor. If that was the case, at least one of the proteins involved in the attachment must be phosphorylated by p34(cdc2) (cdk1). Using confocal microscopy and standard biochemical analysis, we found that p34(cdc2)-mediated phosphorylation indeed released MTOCs from IFs in permeabilized cells. In isolated, immunoprecipitated multiprotein complexes containing both gamma-tubulin and cytokeratin 19, p34(cdc2) phosphorylated only one protein, and phosphorylation released cytokeratin 19 from the complexes. We conclude that this as yet unidentified protein is a part of the molecular mechanism that attaches MTOCs to IFs in interphase.
Figueroa
Yolanda
Y
Department of Cell Biology and Anatomy, University of Miami School of Medicine, Miami, Florida 33101, USA.
Wald
Flavia A
FA
Salas
Pedro J I
PJ
D016203:CDC2 Protein Kinase / Q000187:drug effects / Q000378:metabolism*; D018938:Caco-2 Cells; D018929:Cell Culture Techniques / Q000379:methods; D002463:Cell Membrane Permeability; D006801:Humans; D007382:Intermediate Filaments / Q000378:metabolism* / Q000648:ultrastructure; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000473:pathology; D015739:Nocodazole / Q000494:pharmacology; D010766:Phosphorylation; D012503:Saponins / Q000494:pharmacology
D012503:Saponins; D016203:CDC2 Protein Kinase; D015739:Nocodazole