Cortactin and phagocytosis in isolated Sertoli cells

Cortactin, an actin binding protein, has been associated with Sertoli cell ectoplasmic specializations in vivo, based on its immunolocalization around the heads of elongated spermatids, but not previously identified in isolated Sertoli cells. In an in vitro model of Sertoli cell-spermatid binding, cortactin was identified around debris and dead germ cells. Based on this observation, we hypothesized that this actin binding protein may be associated with a non-junction-related physiological function, such as phagocytosis. The purpose of this study was to identify the presence and distribution of cortactin in isolated rat Sertoli cells active in phagocytic activity following the addition of 0.8 microm latex beads.

Sertoli cell monocultures were incubated with or without follicle stimulating hormone (FSH; 0.1 microg/ml) in the presence or absence of cytochalasin D (2 microM), as an actin disrupter. Cortactin was identified by standard immunostaining with anti-cortactin, clone 4F11 (Upstate) after incubation times of 15 min, 2 hr, and 24 hr with or without beads. Cells exposed to no hormone and no beads appeared to have a ubiquitous distribution of cortactin throughout the cytoplasm. In the presence of cytochalasin D, cortactin immunostaining was punctate and distributed in a pattern similar to that reported for actin in cells exposed to cytochalasin D. Sertoli cells not exposed to FSH, but activated with beads, did not show cortactin immunostaining around the phagocytized beads at any of the time periods. FSH exposure did not alter the distribution of cortactin within Sertoli cells, even when phagocytic activity was upregulated by the presence of beads.

Results of this study suggest cortactin is not associated with peripheralized actin at junctional or phagocytic sites. Further studies are necessary to clarify the role of cortactin in Sertoli cells.