Gelsolin — evidence for a role in turnover of junction-related actin filaments in Sertoli cells Available to Purchase

The gelsolin-phosphoinositide pathway may be part of the normal mechanism by which Sertoli cells regulate sperm release and turnover of the blood-testis barrier. The intercellular adhesion complexes (ectoplasmic specializations)involved with these two processes are tripartite structures consisting of the plasma membrane, a layer of actin filaments and a cistern of endoplasmic reticulum. Gelsolin is concentrated in these adhesion complexes. In addition,phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P₂) and phosphoinositide-specific phospholipase C are found in the structures. Treatment of isolated spermatid/junction complexes with exogenous phosphoinositide-specific phospholipase C, or with a synthetic peptide consisting of the PtdIns(4,5)P₂ binding region of gelsolin, results in the release of gelsolin and loss of actin from the adhesion complexes. We present a model for the disassembly of the actin layer of the adhesion complex that involves the hydrolysis of PtdIns(4,5)P₂ resulting in the release of gelsolin within the plaque. Further, we speculate that the hydrolysis of PtdIns(4,5)P₂ may result in a local Ca²⁺ surge via the action of inositol triphosphate on junctional endoplasmic reticulum. This Ca²⁺ surge would facilitate the actin severing function of gelsolin within the adhesion complex.