Regulation of Pyk2 expression by p56(Lck) in Jurkat T lymphocytes.

Lysates from the Jurkat T lymphocyte cell line were immunoblotted with anti-Pyk2, and two major forms of Pyk2 were identified. When lysates from the p56(Lck) negative (J.CaM1/Rep3) and CD45 negative Jurkat cell line derivatives were immunoblotted with anti-Pyk2, only the lower mobility form of Pyk2 was predominant. Transfection of J.CaM1 cells with p56(Lck) restored expression of the multiple forms of Pyk2. Using RT-PCR, we found that both species of the alternatively spliced mRNA for Pyk2 were present in all of the lines regardless of their ability to express CD45 or p56(Lck) protein. When p56(Lck) immunoprecipitates were immunoblotted with anti-Pyk2, only the higher mobility form of Pyk2 immunoprecipitated with p56(Lck). These data demonstrate that certain members of the Src family of kinases interact preferentially with the different isoforms of Pyk2 and may have a role in the regulation of the Pyk2 protein in lymphocytes.