Identification of novel human tumor cell-specific CaMK-II variants

• Published in: Biochimica et biophysica acta 1997-03, Vol.1355 (3), p.281-292
• Main Authors: Tombes, Robert M, Krystal, Geoffrey W
• Format: Article
• Language: English
• Subjects: Alternative splicing; Alternative Splicing - genetics; Amino Acid Sequence; Blotting, Northern; Blotting, Western; Breast Neoplasms - enzymology; Breast tumor; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Calcium-Calmodulin-Dependent Protein Kinases - chemistry; Calcium-Calmodulin-Dependent Protein Kinases - genetics; Calcium-Calmodulin-Dependent Protein Kinases - metabolism; Calmodulin; CaMK-II; Cerebral Cortex - enzymology; Cloning, Molecular; DNA Primers; Gene Expression; Humans; Isoenzymes - metabolism; Molecular Sequence Data; Neuroblastoma; Neuroblastoma - enzymology; Polymerase Chain Reaction; Protein kinase; Tumor Cells, Cultured
• ISSN: 0167-4889; 0006-3002; 1879-2596
• DOI: 10.1016/S0167-4889(96)00141-3

CaMK-II (the (type II) multifunctional Ca 2+/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 ( α, β, γ and δ) 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 β, γ or δ CaMK-II. They included 2 β isozymes ( β e, β e′), 4 γ isozymes ( γ B, γ C, γ G, γ H) and 2 δ isozymes ( δ C, δ E) This is the first report of human β and δ CaMK-II sequences. A panel of human cell types was then screened for these CaMK-II isozymes. As expected, cerebral cortex predominately expressed α, β and δ 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 α CaMK-II and expressed 1–2 β isozymes, at least 3 γ isozymes and 1–2 δ isozymes. When compared to undifferentiated fibroblasts, β e, β e′, γ G and γ 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.