Expression of V integrin and its potential partners in bull reproductive tissues, germ cells and spermatozoa

Integrins are transmembrane receptors expressed in all nucleated mammalian cells, critically involved in cell-matrix adhesion and cell-cell interactions that modulate many signalling cascades. It is assumed that integrins also provide essential functions of the reproductive system. In this study, we describe the detailed localization and distribution of aV integrin in the plasma membrane of bull sperm head and tail. Integrin aV was observed in the area of forming acrosome in developing sperm since the stage of round spermatids and persists in the acrosome during epididymal maturation and ejaculation till the acrosomal exocytosis. We detected CD9 and CD81 tetraspanins as the potential partners of aV integrin. Their similar staining pattern in testicular tissue suggested the involvement of these molecules in the tetraspanin web of "testisomes". Moreover, the complex of alpha V with beta 1 and beta 3 integrin subunits cannot be excluded at least in sperm. The presented findings contribute to understanding the mutual action of integrins and tetraspanins during sperm development and maturation.