PHOSPHORYLATION OF SHC PROTEINS IN HUMAN SPERM IN RESPONSE TO CAPACITATION AND PROGESTERONE TREATMENT

Several authors have demonstrated the involvement of tyrosine kinases during sperm capacitation and acrosome reaction. Shc proteins (p46(Shc ), p52(Shc), and p66(Shc) are cytoplasmic substrates of activated tyro sine kinases and are widely expressed in mammalian somatic tissues. Ex periments were designed to demonstrate the presence of Shc in spermato zoa and to study its involvement in the signal transduction events lea ding to acrosome reaction. Anti-She antibodies strongly reacted with t he acrosomal region of methanol-fixed human sperm. Only one Shc isofor m (p52(Shc)) was detected on Western blot. To study the degree of phos phorylation of Shc during capacitation and acrosome reaction, sperm sa mples were divided into two groups: noncapacitated and capacitated/pro gesterone treated. Lysates from both groups were immunoprecipitated wi th anti-phosphotyrosine antibodies and the precipitated tie, phosphory lated) proteins were tested with anti-She antibodies. The intensity of p52(Shc) was clearly increased in capacitated/progesterone-stimulated cells. (C) 1998 Wiley-Liss, Inc.