Cooperative regulation of AJM-1 controls junctional integrity in Caenorhabditis elegans epithelia

Abstract

The function of epithelial cell sheets depends on the integrity of specialized cell-cell junctions that connect neighbouring cells. We have characterized the novel coiled-coil protein AJM-1, which localizes to an apical junctional domain of Caenorhabditis elegans epithelia basal to the HMR-HMP (cadherin-catenin) complex. In the absence of AJM-1, the integrity of this domain is compromised. Proper AJM-1 localization requires LET-413 and DLG-1, homologues of the Drosophila tumour suppressors Scribble and Discs large, respectively. DLG-1 physically interacts with AJM-1 and is required for its normal apical distribution, and LET-413 mediates the rapid accumulation of both DLG-1 and AJM-1 in the apical domain. In the absence of both dlg-1 and let-413 function AJM-1 is almost completely lost from apical junctions in embryos, whereas HMP-1 (alpha-catenin) localization is only mildly affected. We conclude that LET-413 and DLG-1 cooperatively control AJM-1 localization and that AJM-1 controls the integrity of a distinct apical junctional domain in C. elegans.

Lipoprotein receptors and a Disabled family cytoplasmic adaptor protein regulate EGL-17/FGF export in C. elegans

“…A similar accumulation of EGL-17ϻGFP in P6.p descendants was observed by using RNAi for subunits of clathrin adaptor complex AP-1, but not AP-2 or AP-3. On the other hand, traffic of LET-23 to the apical surface of the VPCs, and its localization to the basolateral surface by the LIN-2/7/10 complex (Simske et al 1996;Kaech et al 1998;Whitfield et al 1999), appears to be normal, and the protein AJM-1 (Koppen et al 2001) also localizes normally to junctions (Fig. 3).…”

Control of tumourigenesis by the Scribble/Dlg/Lgl polarity module

“…In the worm C. elegans, mutants for either Dlg-1 or Let-413 (the Scribble homologue) have defects in adherens junction formation (Legouis et al, 2000;Bossinger et al, 2001). Dlg-1 is restricted to the adherens junctions, where it physically interacts with the adherens junction marker AJM-1 (Koppen et al, 2001). The disruption to epithelial polarity seen in Let-413-deficient embryos, together with the specific effects seen in Dlg-1-deficient embryos in AJM-1 recruitment to the adherens junctions (McMahon et al, 2001), suggests that in contrast to Drosophila, Let-413 and Dlg-1 apparently have distinct functions.…”

Structural components of the nonstriated contractile apparatuses in the Caenorhabditis elegans gonadal myoepithelial sheath and their essential roles for ovulation

“…We also examined distribution of AJM-1, a component of adherens junctions (Koppen et al, 2001), myotactin, a component of hemidesmosomes (Hresko et al, 1999), UNC-78 actininteracting protein 1 (Ono, 2001), and UNC-60B actin depolymerizing factor/ cofilin (Ono et al, 1999. However, these proteins were detected only in the spermatheca but not in the myoepithelial sheath (our unpublished data).…”