Identification of novel human tumor cell-specific CaMK-II variants.
CaMK-II (the (type II) multifunctional Ca2+/CaM-dependent protein kinase) has been implicated in diverse neuronal and non-neuronal functions, including cell growth control. CaMKII expression was evaluated in a variety of human tumor cell lines using RT-PCR (reverse transcriptase coupled polymerase chain reaction). PCR primers which flanked the CaMK-II variable domain were used so that all possible variants of the four mammalian CaMK-II genes (alpha, beta, gamma and delta) could be identified. 8 distinct CaMK-II isozymes were identified from human mammary tumor and neuroblastoma cell cDNA, each of which represented a variant of beta, gamma or delta CaMK-II. They included 2 beta isozymes (beta e, beta 'e), 4 gamma isozymes (gamma B, gamma C, gamma G, gamma H) and 2 delta isozymes (delta C, delta E) This is the first report of human beta and delta CaMK-II sequences. A panel of human cell types was then screened for these CaMK-II isozymes. As expected, cerebral cortex predominately expressed alpha, beta and delta A CaMK-II. In contrast, tumor cells, including those of neuronal origin, expressed an entirely different spectrum of CaMK-II isozymes than adult neuronal tissue. Tumor cells of diverse tissue origin uniformly lacked alpha CaMK-II and expressed 1-2 beta isozymes, at least 3 gamma isozymes and 1-2 delta isozymes. When compared to undifferentiated fibroblasts, beta e, beta'e, gamma G and gamma H were preferentially expressed in tumor cells. CaMK-II immunoblots also indicated that neuroblastoma and mammary tumor cells express isozymes of CaMK-II not present in their non-transformed cell or tissue counterpart. The identification of these new, potential tumor-specific CaMK-II variants supports previous indications that CaMK-II plays a role in growth control. In addition, these results provide insight into both splice variant switching and variable domain structural similarities among all CaMK-II isozymes.
Tombes
R M
RM
Massey Cancer Center, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298-0037, USA.
Krystal
G W
GW
D017398:Alternative Splicing / Q000235:genetics; D000595:Amino Acid Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000201:enzymology*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002540:Cerebral Cortex / Q000201:enzymology*; D003001:Cloning, Molecular; D017931:DNA Primers; D015870:Gene Expression; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D008969:Molecular Sequence Data; D009447:Neuroblastoma / Q000201:enzymology*; D016133:Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
D017931:DNA Primers; D007527:Isoenzymes; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases