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Cross‐linkage of a receptor on nonspecific cytotoxic cells or treatment with calcium ionophore triggers increased phosphorylation of serine residues
Author(s) -
Evans D. L.,
Leary J. H.,
JasoFriedmann L.
Publication year - 1995
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.1995.tb06045.x
Subject(s) - biology , phosphorylation , serine , immunoprecipitation , phosphoserine , hyperphosphorylation , biochemistry , protein phosphorylation , protein kinase c , microbiology and biotechnology , calcium , tyrosine phosphorylation , protein kinase a , chemistry , organic chemistry , gene
Cross‐linkage of a putative receptor protein on nonspecific cytotoxic cells (NCC) with monoclonal antibody (mab) 5C6 produces: activation of cytotoxicity; increased release of free cytosolic calcium; increased levels of IP3 and IP4; and increased DNA synthesis. Mab‐binding also caused increased expression of various proto‐oncogene kinases and increased expression of tyrosine phosphorylated proteins. In the present study NCC triggering by mab 5C6 was linked to serine specific kinase/phosphatase action. Concomitant with mab 5C6 activation, two proteins of 55‐60 and 25‐30 kDa were hyperphosphorylated on serine residues (15‐30 min post‐activation) determined by immunoprecipitation with an anti‐phosphoserine specific mab. These proteins appeared to be components of a large macromolecular protein complex (> 170 kDa) determined by resolution in reducing and non‐reducing SDS‐PAGE. Sequential immunoprecipitation experiments revealed that these proteins were not PKC or p56 lck . Activation of NCC with the calcium ionophore A23187 caused the expression of this same complex of serine phosphorylated proteins. These data indicate that hyperphosphorylation of serine residues is associated with increased NCC cytotoxicity. Activation may be associated with receptor cross‐linkage or calcium ionophore treatment, both events producing the phosphorylation of the same substrates.