title: Tubulobulbar complexes are intercellular podosome-like structures that internalize intact intercellular junctions during epithelial remodeling events in the rat testis.
abstract: Tubulobulbar complexes are actin-related double-membrane projections that resemble podosomes in other systems and form at intercellular junctions in the seminiferous epithelium of the mammalian testis. They are proposed to internalize intact junctions during sperm release and during the translocation of spermatocytes through basal junction complexes between neighboring Sertoli cells. In this study we probe apical tubulobulbar complexes in fixed epithelial fragments and fixed frozen sections of rat and mouse testes for junction molecules reported to be present at apical sites of attachment (ectoplasmic specializations) between Sertoli cells and spermatids. The adhesion molecules nectin 2 (PVRL2), nectin 3 (PVRL3) and alpha 6 integrin (ITGA6) are present in the elongate parts of tubulobulbar complexes and concentrated at their distal ends. Tubulobulbar complexes contain cortactin (CTTN), a key component of podosomes, and vesicles at the distal ends of tubulobulbar complexes that contain junction molecules are related to early endosome antigen (EEA1). N-cadherin (CDH2), a protein reported to be present at ectoplasmic specializations, is not localized to these unique junctions or to tubulobulbar complexes but, rather, is primarily concentrated at desmosomes in basal regions of the epithelium. Our results are consistent with the conclusion that tubulobulbar complexes are podosome-like structures that are responsible for internalizing intact intercellular junctions during spermatogenesis.
authors.affiliation: Department of Cellular and Physiological Sciences, Faculty of Medicine, Life Sciences Centre, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: J'Nelle S
authors.initials: JS
authors.lastname: Young
authors.forename: Julian A
authors.initials: JA
authors.lastname: Guttman
authors.forename: Kuljeet S
authors.initials: KS
authors.lastname: Vaid
authors.forename: A Wayne
authors.initials: AW
authors.lastname: Vogl
mesh_terms: D022005:Adherens Junctions / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000378:metabolism; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism; D058966:Contactins; D016023:Integrins / Q000378:metabolism; D008297:Male; D008856:Microscopy, Fluorescence; D016253:Microscopy, Immunoelectron; D008858:Microscopy, Phase-Contrast; D000075983:Nectins; D051381:Rats; D017207:Rats, Sprague-Dawley; D012670:Seminiferous Epithelium / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D012708:Sertoli Cells / Q000166:cytology / Q000378:metabolism; D013087:Spermatids / Q000166:cytology / Q000378:metabolism; D013091:Spermatogenesis / Q000502:physiology; D013737:Testis / Q000166:cytology* / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: D015820:Cadherins; D015815:Cell Adhesion Molecules; D015816:Cell Adhesion Molecules, Neuronal; D058966:Contactins; D016023:Integrins; C000619016:Nectin2 protein, mouse; C000619017:Nectin3 protein, mouse; D000075983:Nectins; D033921:Vesicular Transport Proteins; C093846:early endosome antigen 1