Sortilin: a new alternative for the transport of proteins in epididymal cells.

AGUILERA C; BANNOUD N; SOSA MA; CARVELLI L

San Luis

Congreso; XXVII Reunión Anual de la Sociedad de Biología de Cuyo; 2009

Sociedad de Biología de Cuyo

Epididymal cells exhibit a significant secretory activity, and it is thought that participate in maturation of sperm. The intracellular transport of lysosomal proteins is regulated by M6P receptors (MPRS) in most eukaryotic cells,and significant levels of these MPRS were also found in rat epididymis. Acid hydrolases are found in the epididymal fluid due to an active secretion by the epithelium. Cathepsin D, which is secreted into the lumen as the precursor form (PCD), is increased due to hormonal changes. Based on cell models that involve other proteins in the transport and secretion of PCD, we intended to study the incidence of the membrane protein sortilin on transport and secretion of PCD in epididymal cells. We performed an experimental model based on a cell line from rat epididymis (RCE-1), which were depleted of sortilin by gene silencing. The cells were transfected with the plasmid sortilin pSilencer neo (Ambion) to produce stable sortilin siRNA. The  transfected cells were selected with Geneticin and depletion of sortilin was confirmed by IFI and western blot. This silencing affected the expression and localization of other proteins, such as cation-dependent MPR (CD-MPR) and prosaposin, a ligand for sortilin. CD-MPR and prosaposin increased significantly, meanwhile PCD decreased under these conditions. In turn, changes in distribution of prosaposin and CD-MPR were observed by IFI. However, distribution of PCD showed no major changes. These preliminary results suggest that PCD could be transported by sortilin and CD-MPR alternatively.