TABLE 1

Types of cell junctions and their constituent and peripheral proteins found at the blood-testis barrier (BTB) in rodent testes

Prepared based on reviews (Cheng and Mruk, 2002, 2009b, 2010a, 2011; Mruk and Cheng, 2004b, 2010, 2011; Lie et al., 2008, 2011a; Mruk et al., 2008, 2011; Siu and Cheng, 2008; Yan et al., 2008a; Li et al., 2009c; Wong and Cheng, 2009; Kopera et al., 2010; Morrow et al., 2010; Su et al., 2011a) and reports (Li et al., 2011b), many of which are cited in the text.

Junction TypeComponent Proteins
Occluding junction
    Tight junction
        Integral membrane proteinsOccludin, claudin-1, -3, -4, -5, -7, -8, -11, JAM-A, JAM-B, CLMP, CAR
        AdaptorsZO-1, ZO-2, vinculin
        Regulatory or signaling proteinsFAK, c-Src, c-Yes, p38 MAPK, ERK1/2, JNK, PKB (Akt), PAK, PI3K
        Polarity proteinsPAR6, 14–3-3, PATJ, PALS1, Scribble, Crumbs, Cdc42
        ProteaseMMP9
        Protease inhibitorsTIMP-1, α2-macroglobulin
        Trafficking proteinsDynamin 2, Rab8B, clathrin, caveolin-1, EEA-1, Rab9, MTMR2, annexin II
        CytokinesTGF-β2, TGF-β3, TNFα, IL-1α
        Drug transportersP-glycoprotein (efflux pump), Oatp3 (influx pump)
        Scaffolding proteinsActin, collagen α3(IV)
Anchoring junction
    Cell-cell actin-based
        Basal ES
            Integral membrane proteinsN-cadherin, E-cadherin, nectin-2, CAR
            Adaptorsα-catenin, β-catenin, γ-catenin, afadin, vinculin
            Regulatory or signaling proteinsc-Src, c-Yes, CK2, Csk
            Trafficking proteinsDynamin 2, clathrin, caveolin-1, MTMR2, annexin II
            Drug transportersOatp3
            Scaffolding proteinsActin
            Actin regulatory proteinsEps8, Arp2/3 complex, N-WASP, drebrin E
    Cell-cell intermediate filament-based
        Desmosome
            Integral membrane proteinsDesmoglein 2, desmocollin 2, desmocollin 3
            AdaptorsPlakoglobin (γ-catenin), plakophilin-1,- 2,- 4, desmoplakin
            Regulatory or signaling proteinsc-Src, CK2, Csk
            Scaffolding proteinsVimentin
Communicating junction
    Gap junction
            Integral membrane proteinsConnexin-43, -33, -26, -32, -36, -37, -40, -43, -45, -46, -50, -57
            AdaptorsPlakophilin 2, β-catenin, drebrin E
            Regulatory or signaling proteinsc-Src
            Scaffolding proteinsActin

  • CK2, casein kinase 2; CLMP, CXADR-like membrane protein; Csk, carboxyl-terminal Src kinase; drebrin E, developmentally regulated brain protein E; EEA-1, early endosome antigen-1; N-WASP, neuronal Wiskott-Aldrich syndrome protein; PAK, p21-activated kinase; PALS1, protein associated with Lin seven-1; PATJ, Pals1-associated tight junction protein; TIMP-1, tissue inhibitor of metalloproteases-1, a metalloprotease inhibitor.