Mannose 6-phosphate-containing peptides activate phospholipase C in proximal tubular basolateral membranes from...

To ascertain whether mannose 6-phosphate-containing peptides that bind to the insulin-like growth factor II (IGF II)/mannose 6-phosphate receptor activate phospholipase C, we determined the effect of proliferin, transforming growth factor-beta 1 (TGF-beta 1) precursor, and beta-galactosidase on production of inositol trisphosphate (Ins-P3) in basolateral membranes isolated from the renal proximal tubule of dogs. Both proliferin and TGF-beta 1 precursor stimulated Ins-P3 production in a concentration-dependent manner. Maximal production was stimulated by approximately 10(-13) M of each peptide. beta-Galactosidase had no effect on Ins-P3 generation. Neither proliferin nor TGF-beta 1 precursor potentiated IGF II-stimulated Ins-P3 production. Mannose 6-phosphate itself had no effect on Ins-P3 generation. However, mannose 6-phosphate potentiated production stimulated by 10(-11) M proliferin or 10(-11) M TGF-beta 1 precursor while inhibiting production stimulated by 10(-14) M of either peptide. Addition of anti-mannose 6-phosphate receptor antibodies to basolateral membranes abolished proliferin and TGF-beta 1 precursor-stimulated Ins-P3 generation. We conclude that, in addition to IGF II, mannose 6-phosphate-containing ligands for the IGF II/mannose 6-phosphate receptor activate basolateral membrane phospholipase C. Such activation could reflect a common mechanism for signal transduction by these peptides mediated via the IGF II/mannose 6-phosphate receptor.