Basement membrane diversification relies on two competitive secretory routes defined by Rab10 and Rab8 and modulated by dystrophin and the exocyst complex

Abstract

The basement membrane (BM) is an essential structural element of tissues, and its diversification participates in organ morphogenesis. However, the traffic routes associated with BM formation and the mechanistic modulations explaining its diversification are still poorly understood. Drosophila melanogaster follicular epithelium relies on a BM composed of oriented BM fibrils and a more homogenous matrix. Here, we determined the specific molecular identity and cell exit sites of BM protein secretory routes. First, we found that Rab10 and Rab8 define two parallel routes for BM protein secretion. When both routes were abolished, BM production was fully blocked; however, genetic interactions revealed that these two routes competed. Rab10 promoted lateral and planar-polarized secretion, whereas Rab8 promoted basal secretion, leading to the formation of BM fibrils and homogenous BM, respectively. We also found that the dystrophin-associated protein complex (DAPC) associated with Rab10 and both were present in a planar-polarized tubular compartment containing BM proteins. DAPC was essential for fibril formation and sufficient to reorient secretion towards the Rab10 route. Moreover, we identified a dual function for the exocyst complex in this context. First, the Exo70 subunit directly interacted with dystrophin to limit its planar polarization. Second, the exocyst complex was also required for the Rab8 route. Altogether, these results highlight important mechanistic aspects of BM protein secretion and illustrate how BM diversity can emerge from the spatial control of distinct traffic routes.

Wnt-Ror-Dvl signalling and the dystrophin complex organize planar-polarized membrane compartments inC. elegansmuscles

“…Finally, in drosophila, dystrophin is polarized in epithelial migrating cells, where it is found in the posterior half of cells in a complex pattern, illuminating both the cell cortex and filamentous structures partially aligned with F-actin stress fibers 71 . Functional studies have found that the DAPC promotes planar polarization of integrin clusters and participates in the trafficking of ECM components leading to the formation of polarized fibrils 72 .…”

The Dystrophin-Dystroglycan complex ensures cytokinesis efficiency inDrosophilaepithelia

“…To further validate Dys role in cytokinesis efficiency, we used an optogenetic approach (lightactivated reversible inhibition by assembled trap (LARIAT)) that enables temporally-controlled disruption of protein function by light-induced clustering of endogenously GFP-tagged proteins (Osswald et al, 2022;Qin et al, 2017). To target Dys, we used flies with endogenously sfGFP:tagged Dys, which labels all Dys isoforms (Dennis et al, 2023), and co-expressed GAL4-driven UAS-LARIAT (UAS-VHH:CRY2-P2A-CIBN:MP) in the follicular epithelium (Fig 2D). We first confirmed that blue light exposure of egg chambers cultured ex vivo quickly induces Dys:sfGFP clustering in the basal cortex of follicle cells (Fig 2E).…”