title: p-FAK-Tyr(397) regulates spermatid adhesion in the rat testis via its effects on F-actin organization at the ectoplasmic specialization.
abstract: During spermatogenesis, the molecular mechanism that confers spermatid adhesion to the Sertoli cell at the apical ectoplasmic specialization (apical ES), a testis-specific F-actin-rich adherens junction, in the rat testis remains elusive. Herein, the activated form of focal adhesion kinase (FAK), p-FAK-Tyr(397), a component of the apical ES that was expressed predominantly and stage specifically in stage VII-early stage VIII tubules, was found to be a crucial apical ES regulator. Using an FAK-Y397E phosphomimetic mutant cloned in a mammalian expression vector for its transfection vs. FAK and vector alone in adult rat testes in vivo, its overexpression was found to cause defects in spermiation. These defects in spermiation were manifested by entrapment of spermatids in the seminiferous epithelium in late stage VIII-X tubules and were mediated by a disruption on the spatiotemporal expression and/or mislocalization of actin regulatory protein actin-related protein 3, which induces branched actin polymerization, epidermal growth factor receptor pathway substrate 8 (an actin barbed end capping and bundling protein), and palladin (an actin cross-linking and bundling protein). This thus perturbed changes of F-actin organization at the apical ES to facilitate spermiation, which also led to a concomitant alteration in the distribution and upregulation of adhesion proteins nectin-2 and nectin-3 at the apical ES. As such, nectin-2 and -3 remained at the apical ES to anchor step 19 spermatids on to the epithelium, delaying spermiation. These findings illustrate a mechanistic pathway mediated by p-FAK-Tyr(397) that regulates spermatid adhesion at the apical ES in vivo.
authors.affiliation: The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, New York;
authors.forename: Hin-Ting
authors.initials: HT
authors.lastname: Wan
authors.forename: Dolores D
authors.initials: DD
authors.lastname: Mruk
authors.forename: Stephen Y T
authors.initials: SY
authors.lastname: Li
authors.forename: Ka-Wai
authors.initials: KW
authors.lastname: Mok
authors.forename: Will M
authors.initials: WM
authors.lastname: Lee
authors.forename: Chris K C
authors.initials: CK
authors.lastname: Wong
authors.forename: C Yan
authors.initials: CY
authors.lastname: Cheng
mesh_terms: D008841:Actin Cytoskeleton / Q000235:genetics / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D000818:Animals; D030801:Animals, Genetically Modified; D001814:Blood-Testis Barrier / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology*; D051417:Focal Adhesion Kinase 1 / Q000235:genetics / Q000378:metabolism*; D008297:Male; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012670:Seminiferous Epithelium / Q000166:cytology / Q000378:metabolism; D012708:Sertoli Cells / Q000378:metabolism; D013087:Spermatids / Q000166:cytology / Q000378:metabolism*; D013091:Spermatogenesis / Q000502:physiology*; D013737:Testis / Q000378:metabolism / Q000502:physiology*; D014443:Tyrosine / Q000378:metabolism
chemical_list: D000199:Actins; D014443:Tyrosine; D051417:Focal Adhesion Kinase 1; C496052:Ptk2 protein, rat
keywords: actin filament bundles; adherens junction; focal adhesion kinase; focal adhesion kinase mutant; spermatogenesis; testis