Molecular cloning and characterization of a novel calcium/calmodulin-dependent protein kinase II inhibitor from human dendritic cells

Calcium/calmodulin-dependent protein kinase II (CaMKII) is a widely distrib uted protein kinase that regulates numerous physiological functions. Inhibi tors of CaMKII are useful tools for investigating the CaMKII functions. Her e we identified a novel (CaMKII inhibitor protein (CaM-KIIN) from the human dendritic cell cDNA library by large-scale random sequencing. Human CaM-KI IN contains 79 amino acids, which shares 98% identity and 98% positives wit h rat CaMKII inhibitor protein beta and 65% identity and 78% positives with rat CaMKII inhibitor alpha. Human CaM-KIIN mRNA expression was detectable in various tissues and cell lines by Northern blot and RT-PCB, To investiga te its biological functions, full-length human CaM-KIIN was overexpressed i n colon adenocarcinoma LoVo cells. When expressed in LoVo cells, it could i nhibit cell proliferation, block cell growth, and decrease the viable cell number. These results characterize a potential cellular inhibitor protein o f CaMKII that plays an important role in the regulation of cell growth. (C) 2001 Academic Press.