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  • Title: Induction of MAPK phosphorylation by prosaposin and prosaptide in PC12 cells.
    Author: Campana WM, Hiraiwa M, Addison KC, O'Brien JS.
    Journal: Biochem Biophys Res Commun; 1996 Dec 24; 229(3):706-12. PubMed ID: 8954961.
    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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