The serum-inducible protein kinase Snk is a G1 phase polo-like kinase that is inhibited by the calcium- and integrin-binding protein CIB.
Identified as an immediate-early transcript, the serum-inducible kinase Snk bears sequence homology with the polo-like kinases. Endogenous Snk was detected in early G(1) in NIH 3T3 cells, and nascent Snk showed a half-life of about 15 min. The kinase activity of endogenous Snk was detected in G(1). Substitution of Thr-236 with a glutamate residue increased Snk kinase activity by about 10-fold, whereas substitution of Lys-108 abolished its kinase activity. Disrupting the polo-box did not significantly change Snk kinase activity. A GFP-C-Snk fusion protein showed polo-box-dependent localization to the microtubule organizing center, and ectopic expression of Snk in COS-7 cells induced changes in cell morphology, depending on Snk kinase activity and the polo-box. The capacity of Snk to induce morphological changes was inhibited by the calcium- and integrin-binding protein CIB. CIB co-immunoprecipitated with Snk and inhibited the kinase activity of Snk, suggesting that CIB is a negative regulator for Snk kinase activity.
Ma
Sheng
S
The Biological Laboratories, Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA. shengma@fas.harvard.edu
Liu
Mei-Ann
MA
Yuan
Yi-Lu O
YL
Erikson
Raymond L
RL
D016475:3T3 Cells; D000818:Animals; D019556:COS Cells; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins; D004789:Enzyme Activation / Q000502:physiology; D016193:G1 Phase / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic; D051379:Mice; D011233:Precipitin Tests; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D000097869:Polo-Like Kinase 1
D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D000097869:Polo-Like Kinase 1; C491605:Cib1 protein, mouse; C444640:serum-inducible kinase