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Updated: Jul 20, 2026

Focal Ca2+ Transient Detection in Smooth Muscle
Published on: June 29, 2009
Calcium-modulated rod outer segment membrane guanylate cyclase type 1 transduction machinery in the testes
Anna Jankowska1, Beata Burczynska, Teresa Duda
1Department of Cell Biology, University of Medical Sciences, Poznan, Poland. ajanko@amp.edu.pl
Abstract:
The importance of the second messengers, Ca(2+) 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 Ca(2+)-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.
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