Cortactin/tyrosine‐phosphorylated cortactin interaction with connexin 43 in mouse seminiferous tubules

Abstract

Deletion of the cortactin gene leads to male infertility. Considering that cortactin is an actin filament (F-actin)-binding protein associated with intercellular junctions, we measured changes in the expression and distribution of cortactin and tyrosine phosphorylated cortactin (P-cortactin) in the seminiferous epithelium of developing and adult mice to address the physiological significance of cortactin to germ cell differentiation. Cortactin was expressed in neonatal and developing Sertoli cells. Cortactin levels decreased early during puberty, while P-cortactin increased. Cortactin labeling was intense in the basal and apical thirds of the epithelium. Sertoli cell cytoplasmic processes facing spermatogonia, preleptotene spermatocytes, and step 8-13 spermatids were intensely labeled by both cortactin and P-cortactin. In contrast, the middle region of Sertoli cells exhibited diffuse cortactin labeling but no P-cortactin. This is consistent with the view that plasma membrane segments facing germ cells are part of the continuum of Sertoli cell junctional complexes that extend over lateral and apical membranes of supporting cells. Moreover, F-actin and P-cortactin share a common location in the seminiferous epithelium. The increased P-cortactin levels detected during puberty may be related to the modulatory effect of cortactin tyrosine phosphorylation on actin assembly at sites of selected Sertoli cell-germ cell contacts. Cortactin and connexin 43 (Cx43) were physically linked in seminiferous tubule homogenates and their colocalization in the basal and apical thirds of the seminiferous epithelium was stage-dependent. Our results suggest that cortactin-Cx43 interaction helps coordinate formation of cell-to-cell junctions and organization of the subsurface actin cytoskeleton in specific regions of the epithelium.

CX43 expression, phosphorylation, and distribution in the normal and autoimmune orchitic testis with a look at gap junctions joining germ cell to germ cell

“…Our observation of a high Cx43 gene expression was matched with Cx43 protein levels that decreased from 210 -270 days and from December-March in normal mink tubules confirms our earlier report of total Cx43 levels falling with adulthood in mouse tubules (84). This decrease in Cx43 protein levels despite elevated Cx43 mRNA levels signifies that either lesser Cx43 protein amounts were synthesized or greater amounts were lost through degradation or through other means during these periods.…”

Functional interaction between TRPC1 channel and connexin-43 protein: a novel pathway underlying S1P action on skeletal myogenesis

“…It has been previously reported by our group and others that actin-binding proteins provide a physical linkage between Cx43 and the cortical cytoskeleton and that these interactions are required for maintaining functional Cx43-formed gap junctions in differentiating myoblasts [6,58]. Among the different proteins interacting with connexins are the ZO proteins, vinculin, ezrin, a-actin and cortactin [6,47,58]. In this study we showed that TRPC1 channels could regulate the remodeling of a specific pool of Cx43 protein, likely through the stabilization and coordination of its interaction with cortactin.…”

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 2: Changes in spermatid organelles associated with development of spermatozoa

“…It consists of F-actin [ID: T2-193], Sak57 an ortholog of keratin 5 [ID: T2-194], myosin , an actin based motor protein, and cortactin (Kierszenbaum et al, 2008). Several reports, however, have shown that only Sertoli cells express cortactin and that it is localizes to these cells in the developing and adult testis (Anahara et al, 2006;Chapin et al, 2001;Kai et al, 2004;Vitale et al, 2009), in contrast to claims that P-cortactin occupies the subacrosomal space of round spermatids (Kierszenbaum et al, 2008). RAB27A and RAB27B are present in the Golgi apparatus and marginal rim of the acroplaxome region.…”