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. 1996 Dec 24;229(3):706-12.
doi: 10.1006/bbrc.1996.1869.

Induction of MAPK phosphorylation by prosaposin and prosaptide in PC12 cells

W M Campana  1 , M Hiraiwa, K C Addison, J S O'Brien
Affiliations

Induction of MAPK phosphorylation by prosaposin and prosaptide in PC12 cells

W M Campana et al. Biochem Biophys Res Commun. .

Abstract

Prosaposin is a 66 kDa glycoprotein which has neurotrophic activity in vitro and in vivo. The neurotrophic sequence (8CEFLVKEVTKLIDNNKTEKEI29L) within prosaposin has been located to the amino terminal portion of the saposin C domain. This 22-mer peptide, prosaptide, has neurotrophic activity equivalent to prosaposin. We present binding studies using 125I-prosaposin and 125I-prosaptide which revealed a single class of specific binding sites with a Kd of 2.5 nM and 18.3 nM, respectively. Both prosaposin and prosaptide rapidly stimulated protein tyrosine phosphorylation in PC12 cells and increased phosphorylation of MAPK 20-fold especially of p44 MAPK which peaked at 5 minutes of stimulation and then rapidly declined. Treatment of PC12 cells with a mutant 22-mer prosaptide (21Asn to 21Asp) did not induce phosphorylation. These findings suggest a role for MAPK in signal transduction by prosaposin.

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