EXPRESSION OF EXOGENOUS P59(FYN) MODULATES SIGNALING IN AN IMMATURE B-CELL LINE, WEHI-231

The WEHI-231 B lymphoma line is representative of immature B cells, wh ich undergo growth arrest/apoptosis following cross-linking of surface immunoglobulin M (sIgM). In B cells, sIgM engagement has been shown t o induce immediate (within seconds) activation of src family protein t yrosine kinases (PTKs) such as p53(lyn)/56(lyn), p55(blk), p56(Ick) an d p59(fyn) which are associated with B cell antigen receptor (BCR) com plex. However, p59(fyn) expression is very low in both normal immature B cells and apoptosis-prone B cell lines, including WEHI-231. Such a finding prompted us to investigate the effects of ectopic expression o f p59(fyn) in growth regulation of WEHI-231 cells. We have obtained WE HI-231 transfectants expressing the exogenous p59(fyn) by retroviral m ediated gene transfer method. The transfectants demonstrated increased [Ca2+](i) level in both the non-stimulated condition and sIgM cross-l inking. The expression of ectopic p59(fyn) also increased the sensitiv ity of the transfectants to growth arrest signal by sIgM cross-linking . The results suggest that p59(fyn) can modulate signal transduction a rid growth regulation when expressed in the immature B cell line.