RESISTANCE TO ANTI-IGM-INDUCED APOPTOSIS IN A WEHI-231 SUBLINE IS DUETO INSUFFICIENT PRODUCTION OF CERAMIDE

We describe the properties of a physiological cell death (PCD)-resista nt subline of WEHI-231 generated from the PCD-susceptible WEHI-231.7 J M cell line maintained in our laboratory. The PCD-resistant WEHI-231.7 JMRE subline was uniquely resistant to anti-immunoglobulin (Ig)M-indu ced PCD but not to irradiation and etoposide. In these sublines, we co mpared the expression of genes implicated in regulating PCD. Northern analysis of c-myc, c-fos, egr-1, Fas, p53 and retinoblastoma revealed similar basal levels of expression in all sublines tested and comparab le responses to anti-IgM treatment. Similarly, the expression of bcl-2 , bcl-x, bar and IL-1 beta converting enzyme did not correlate with su sceptibility to anti-IgM-induced PCD. Next, we systematically studied signal transduction events including: tyrosine phosphorylation, Ca++ f lux, and ceramide production in the JM and JMRE sublines. The tyrosine phosphorylation patterns and the Ca++ influx generated following sIgM engagement were very similar in the JM and JMRE sublines. In contrast , the generation of ceramide differed in the PCD-resistant and PCD-sus ceptible sublines. Ceramide is produced following cross-linking sIgM o n WEHI-231.7 JM cells and causes PCD. Ceramide levels in anti-IgM-trea ted WEHI-231.7 JMRE cells are low and appear to be insufficient to ind uce PCD.