IMMUNOLOCALIZATION OF CYTOPLASMIC AND MYELIN MCALPAIN IN TRANSFECTED SCHWANN-CELLS .1. EFFECT OF TREATMENT WITH GROWTH-FACTORS

We have examined the effect of growth factors on the activity and loca lization of calpain in transfected Schwann cells (tSc), Axolemma-enric hed fraction, cAMP, or NGF showed concentration-dependent inhibition o f both mu calpain and mcalpain activity, In contrast, both acidic FGF and basic FGF stimulated mu calpain (37%) and mcalpain (58%) of tSc wh ile PDGF-aa and PDGF-bb inhibited both calpain activities, The inhibit or (calpastatin) activity was approximately 90% following treatment wi th NGF, cAMP, PDGF-aa, and PDGF-bb compared to control while this acti vity was 40% with FGF-treated samples, Immunofluorescence studies indi cated localization of cytoplasmic calpain in the nuclear region follow ing growth factor treatment in the cytoplasm, Growth factor treatment caused a decrease in the intensity of calpain immunoreactivity, Treatm ent with cAMP or FGF resulted in strong immunoreactivity of mcalpain i n the nuclear region and cytoplasm compared to untreated, The growth f actors did not cause translocation of calpain to the outer surface of the cell membrane, The increased immunoreactivity seen with myelin cal pain antibody was greater than cytosolic antibody, The changes seen in calpain activity and immunoreactivity following treatment with growth factors suggest that these factors may regulate calpain-calpastatin e xpression and translocation to the membrane for interaction with lipid s for enzyme activation. (C) 1997 Wiley-Liss, Inc.