p94^fer facilitates cellular recovery of gamma irradiated pre-T cells

Abstract

p94^fer is a ubiquitous, nuclear and cytoplasmic tyrosine kinase, whose accumulation has been demonstrated in all mammalian cell lines analysed. In the present work, the p94^fer expression profile was determined in cell lines which were not tested before. While being present in several hematopoietic and non hematopoietic cell lines including thymic stromal cells, the p94^fer kinase could not be detected in pre-T and T cell lines. p94^fer was also absent in pre-B line, but accumulated in these cells upon their induced development to antibody producing cells. This is in agreement with the absence of p94^fer in primary thymic and splenic T lymphocytes and its induced accumulation in stimulated B cells. Relatively high p94^fer levels were detected in primary thymic and splenic stromal cells. Ectopic expression of p94^fer in pre-T cells slightly affected their cell cycle profile but it did not affect their apoptotic death which was induced by ionizing radiation. However, p94^fer facilitated dramatically, the cellular recovery of gamma irradiated pre-T cells which have escaped the apoptotic death. The enhanced recovery of the irradiated, p94^fer expressing pre-T cells, resulted most probably from their increased survival, rather than from a prominent change in their proliferation rate. The absence of p94^fer from pre-B and pre-T cells, may thus contribute to the relative sensitivity of these cells to ionizing radiation and to their dependence on the functioning of other nuclear tyrosine kinasese.