A Ca2+/calmodulin-dependent protein kinase, CaM kinase-Gr, expressed after transformation of primary human B lymphocytes by Epstein-Barr virus (EBV) is induced by the EBV oncogene LMP1.
CaM kinase-Gr is a multifunctional Ca2+/calmodulin-dependent protein kinase which is enriched in neurons and T lymphocytes. The kinase is absent from primary human B lymphocytes but is expressed in Epstein-Barr virus (EBV)-transformed B-lymphoblastoid cell lines, suggesting that expression of the kinase can be upregulated by an EBV gene product(s). We investigated the basis of CaM kinase-Gr expression in EBV-transformed cells and the mechanisms that regulate its activity therein by using an EBV-negative Burkitt lymphoma cell line, BJAB, and BJAB cells converted to expression of individual EBV proteins by single-gene transfer. CaM kinase-Gr expression was upregulated in BJAB cells by EBV latent-infection membrane protein 1 (LMP1) but not by LMP2A or by nuclear proteins EBNA1, EBNA2, EBNA3A, and EBNA3C. In LMP1-converted BJAB cells, the kinase was functional and was dramatically activated upon cross-linking of surface immunoglobulin M. Overlapping cDNA clones that encode human CaM kinase-Gr were sequenced, revealing 81% amino acid identity between the rat and human proteins. Transfection of BJAB cells with an expression construct for the human enzyme resulted in a functional kinase which was shown by epitope tagging to localize primarily to cytoplasmic and perinuclear structures. Induction of CaM kinase-Gr expression by LMP1 provides the first example of a Ca2+/calmodulin-dependent protein kinase upregulated by a viral protein. In view of the key role played by LMP1 in B-lymphocyte immortalization by EBV, these findings implicate CaM kinase-Gr as a potential mediator of B-lymphocyte growth transformation.
Mosialos
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Department of Medicine, Harvard Medical School, Boston, Massachusetts.
Hanissian
S H
SH
Jawahar
S
S
Vara
L
L
Kieff
E
E
Chatila
T A
TA
D000595:Amino Acid Sequence; D000818:Animals; D000956:Antigens, Viral / Q000494:pharmacology*; D001402:B-Lymphocytes; D001483:Base Sequence; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000737:chemistry; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003432:Cross-Linking Reagents; D003593:Cytoplasm / Q000737:chemistry; D004789:Enzyme Activation; D004790:Enzyme Induction; D005455:Fluorescent Antibody Technique; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D004854:Herpesvirus 4, Human; D006801:Humans; D007075:Immunoglobulin M / Q000378:metabolism; D008969:Molecular Sequence Data; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis; D017386:Sequence Homology, Amino Acid; D014763:Viral Matrix Proteins / Q000494:pharmacology*
D000956:Antigens, Viral; D003432:Cross-Linking Reagents; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D007075:Immunoglobulin M; D011947:Receptors, Antigen, B-Cell; D011994:Recombinant Proteins; D014763:Viral Matrix Proteins; C517683:CAMK4 protein, human; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C517686:Camk4 protein, rat