Crosstalk between desmoglein-2/desmocollin-2/Src kinase and coxsackie and adenovirus receptor/ZO-1 protein complexes, regulates blood-testis barrier dynamics

Abstract

Morphological studies in the testis reported the presence of 'desmosome-like' junctions between Sertoli cells at the blood-testis barrier, whose function is also constituted by tight junctions and basal ectoplasmic specializations. Unfortunately, little is known about the role of desmosomes in bloodtestis barrier dynamics. This study aims to fill this gap with the functional investigation of two desmosomal cadherins, desmoglein-2 and desmocollin-2, by their specific knockdown in Sertoli cells cultured in vitro. Reminiscent of the blood-testis barrier in vivo, desmosome-like structures were visible by electron microscopy when Sertoli cells were cultured at high density, thereby forming a polarized epithelium with functional cell junctions. At this point, we opted to focus our efforts on desmoglein-2 and desmocollin-2 based on results which illustrated desmosomal mRNAs to be expressed by Sertoli and germ cells, as well as on results which illustrated desmoglein-2 to coimmunoprecipitate with plakoglobin, c-Src and desmocollin-2. Simultaneous knockdown of desmoglein-2 and desmocollin-2 not only led to a reduction and mislocalization of zonula occludens-1, but also perturbed the localization of c-Src and coxsackie and adenovirus receptor at the cell-cell interface, resulting in disruption of tight junction permeability barrier. We hereby propose a novel regulatory protein complex composed of desmoglein-2, desmocollin-2, c-Src, coxsackie and adenovirus receptor and ZO-1 at the blood-testis barrier.

Connexin 43 is critical to maintain the homeostasis of the blood–testis barrier via its effects on tight junction reassembly

“…A recent study showed that apart from TJs and basal ES, the desmosome is crucial to maintain the integrity of the Sertoli cell TJ-barrier at the BTB (31). A simultaneous knockdown of desmosome integral membrane proteins desmoglein-2 and desmocollin-2 by RNAi disrupted the Sertoli cell-permeability barrier and affected protein distribution of ZO-1 and CAR at the Sertoli-Sertoli cell interface (31). Furthermore, as discussed above, simultaneous knockdown of Cx43 and plakophilin-2 (a desmosome protein) perturbed the TJ-permeability barrier (7).…”

Focal adhesion kinase-Tyr 407 and -Tyr 397 exhibit antagonistic effects on blood–testis barrier dynamics in the rat

“…Having established that the BTB is a major site where FAK-Tyr 407 but not -Tyr 397 is phosphorylated, a series of experiments was conducted to examine the function of Tyr 407 phosphorylation in BTB dynamics. As a model system, primary Sertoli cells were cultured in vitro under conditions that allow the assembly of a functional TJ barrier with ultrastructures (e.g., TJ, basal ES, gap junction, desmosome) mimicking the BTB in vivo (15,16); this system is widely used in the field (1, 16). Nonphosphorylatable and phosphomimetic mutants at Tyr 407 and/or Tyr 397 were constructed by site-directed mutagenesis in which the Tyr residue was replaced by Phe (Y407F; Y397F) and Glu (Y407E; Y397E), respectively ( and WT FAK serving as controls.…”

“…For instance, in Sertoli cells cultured for increasing periods of time to allow the establishment of TJ and basal ES to create the functional TJ barrier that mimics the BTB in vivo (15,16), both total FAK and p-FAK-Tyr 407 were most highly expressed in freshly isolated cells and showed decreasing protein levels throughout the culture period, whereas p-FAK-Tyr 397 showed an increasing trend from its lowest level in freshly isolated cells ( Fig. 2 A and B).…”

Oncolytic adenovirus modified with somatostatin motifs for selective infection of neuroendocrine tumor cells

“…DSG2 is a component of the cell-cell adhesion structure, which may cross-talk with the CAR molecule within junctional complexes. 18 Similarly to CAR, DSG2 expression has been found in normal epithelial tissues and epithelial cancers. Considering the fact that CAR is often downregulated in tumors, more studies are needed to investigate DSG2 expression pattern in human cancers.…”