Testin Is Tightly Associated with Testicular Cell Membrane upon Its Secretion by Sertoli Cells whose Steady-state mRNA Level in the Testis Correlates with the Turnover and Integrity of Inter-testicular Cell Junctions

Abstract

Testin, a Sertoli cell secretory protein whose mRNA is predominantly expressed in the testis, was shown to become tightly associated with Sertoli cell membrane upon its secretion whose solubilization requires the use of a detergent such as SDS. In the in vitro studies using Sertoli cells cultured at high cell density, where specialized junctions were being formed, the concentration of "soluble" testin in the spent media was greatly reduced versus monolayer cultures at low cell density, where specialized junctions were absent. Conversely, the concentration of "membrane-bound" testin from detergentsolubilized Sertoli cell membrane extract was positively correlated to the existence of specialized junctions in these cultures. In normal rat testes, the level of radioimmunoassayable soluble testin in the cytosol was low. However, when the inter-testicular cell junctions were disrupted either by a drug treatment such as lonidamine in vivo or by a physical treatment in vitro such as exposing Sertoli-germ cell co-cultures where specialized junctions were formed to a hypotonic treatment, a drastic surge in the testin gene expression was noted. Thus, testin can become tightly associated with Sertoli cell membrane upon its secretion when intercellular junctions are formed. It is also a marker to monitor the integrity of inter-testicular cell junctions.

Unraveling the molecular targets pertinent to junction restructuring events during spermatogenesis using the Adjudin-induced germ cell depletion model

“…The identified genes include those that are involved in signaling and/or regulatory functions pertinent to the junction restructuring: (1) cell-cell communication, including cytokine-mediated signaling, ion transport and homeostasis; (2) intracellular signaling mediated via kinases, phosphatase, and adaptors; (3) structurally important cell adhesion and , testin, and claudin 3 respectively, similar to those shown in (A). The induction of testin during Adjudin-induced germ cell loss from the testis is consistent with earlier reports (Grima et al 1997, but changes of a 2 -MG and cathepsin or the unresponsiveness of claudin 3 have not been reported.…”

Coxsackie and adenovirus receptor (CAR) is a product of Sertoli and germ cells in rat testes which is localized at the Sertoli–Sertoli and Sertoli–germ cell interface

“…Sertoli cells-Sertoli cells were isolated from 20-day-old rats as previously described [21]. Freshly isolated cells were cultured at high cell density (0.5 × 10 6 cells/cm 2 ) on Matrigel (BD Biosciences)-coated 12-well dishes (effective surface area, 3.83 cm 2 per well containing 3 mL medium, with ~2×10 6 Sertoli cells).…”

Cysteine Peptidases of Mammals: Their Biological Roles and Potential Effects in the Oral Cavity and Other Tissues in Health and Disease

“…In the ovary, the levels change during the estrus cycle, with the highest levels coincident with the highest rate of junction turnover. Thus, high testin levels are generally associated with disassembly of certain cell-cell junctions (Grima et al, 1997(Grima et al, , 1998. The lack of peptidase or inhibitory activity has been presumed to mean that testin does not mediate cell junction damage or provide tissue protection, and studies with agents that disrupt Sertoli-germ cell junctions indicate that it is unlikely that it functions to re-assemble the junctions.…”