Calcium-modulated rod outer segment membrane guanylate cyclase type 1 transduction machinery in the testes

Abstract

The importance of the second messengers, Ca2+ and cyclic GMP, for the process of fertilization is well established; the mechanisms for their intracellular regulations in the testes are, however, poorly understood. This study documents the biochemical, molecular, and functional identity of a Ca 2+-modulated membrane guanylate cyclase transduction machinery in bovine testes. The machinery is both inhibited and stimulated by free Ca 2+ levels. The Ca2+- sensor component of the inhibitory mode of the machinery is GCAP1 (guanylate cyclase activating protein type 1) and for the stimulatory mode is S100B. The transduction component is a Ca 2+-driven rod outer segment membrane guanylate cyclase type 1, ROS-GC1. The cyclase is predominantly expressed in spermatogenic cells. GCAP1 expression is restricted to a small population of spermatogonia, whereas S100B is present in the majority of spermatocytes and spermatids. The expression of GCAP1 and S100B in spermatocytes and spermatids is mutually exclusive. Copyright © American Society of Andrology.