Differential expression of calmodulin-binding proteins in B, T lymphocytes and thymocytes

Randall L. Kincaid, Hajime Takayama, Melvin L. Billingsley, Michail V. Sitkovsky

Research output: Contribution to journalArticlepeer-review

71 Scopus citations


Changes in intracellular free Ca2+ are involved in the transmembrane signalling of different cells, including lymphocytes 1-3. Since calmodulin (CaM) is a primary receptor for Ca2+ (ref. 4), it may mediate the activation of crucial enzymes after antigen-induced increases in cytosolic Ca2+. Using a biotinylated-CaM (Bio-CaM) detection procedure5 to identify such proteins, we found that a peptide of relative molecular mass 59,000 (59K) was the predominant soluble CaM-binding protein (CaM-BP) in T cells and B lymphocytes from murine spleen; immunoblotting experiments identified it as a subunit of the CaM-dependent phosphatase, 'calcineurin' (CN)6. Smaller amounts of larger CaM-BPs, thought to be cytoskeletal-binding proteins, were also detected. CaM-BPs were expressed differentially, with B lymphocytes having four times more of the CN-like protein than T lymphocytes, while in thymocytes, a 65K polypeptide was the major CaM-BP. However, limited proteolysis analysis suggested that this thymus-specific peptide may be a precursor of CN. These data suggest that Ca2+-stimulated protein dephosphorylation may be an important and highly regulated function in lymphoid cells.

Original languageEnglish (US)
Pages (from-to)176-178
Number of pages3
Issue number6144
StatePublished - 1987

All Science Journal Classification (ASJC) codes

  • General


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