G(1) CELL-CYCLE ARREST AND APOPTOSIS ARE INDUCED IN NIH 3T3 CELLS BY KN-93, AN INHIBITOR OF CAMK-II (THE MULTIFUNCTIONAL CA2+ CAM KINASE)/

CaMK-II (the type II multifunctional Ca2+/calmodulin kinase) is a ubiq uitous serine/threonine protein kinase that is activated by Ca2+ and c almodulin (CaM) and has been implicated in cell cycle control. NIH 3T3 fibroblast cytosolic extracts contain CaMK-II enzymatic activity and two major Ca2+/CaM-dependent phosphoproteins of M(r) 55,000 and 115,00 0. Reverse transcription-PCR indicates that the gamma(B) and gamma(C) isozymes of CaMK-II are predominately expressed. KN-93, a novel membra ne-permeant synthetic inhibitor of purified neuronal CaMK-II, inhibits serum-induced fibroblast cell growth in a comparable dose-dependent f ashion to its inhibition of CaMK-II activity. After 2 days of KN-93 tr eatment, 95% of cells are arrested in G(1). G(1) arrest is reversible; 1 day after KN-93 release, a peak of cells had progressed into S and G(2)-M. KN-92, a similar but inactive compound, had no effect on CaMK- II activity or cell growth. KN-93 also blocked cell growth stimulated by basic fibroblast growth factor, platelet-derived growth factor-BE, epidermal growth factor, and insulin-like growth factor-1. After 3 day s of KN-93-induced G(1) arrest, cell size and viability decreased and DNA fragmented, indicating apoptosis. These data suggest that CaMK-II is necessary for cell cycle progression through G(1) and operates at a site common to the transduction oi signals from growth and/or surviva l factors.