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Smoothelin-like 2 Inhibits Coronin-1B to Stabilize the Apical Actin Cortex during Epithelial Morphogenesis.

ABSTRACT: The actin cortex is involved in many biological processes and needs to be significantly remodeled during cell differentiation. Developing epithelial cells construct a dense apical actin cortex to carry out their barrier and exchange functions. The apical cortex assembles in response to three-dimensional (3D) extracellular cues, but the regulation of this process during epithelial morphogenesis remains unknown. Here, we describe the function of Smoothelin-like 2 (SMTNL2), a member of the smooth-muscle-related Smoothelin protein family, in apical cortex maturation. SMTNL2 is induced during development in multiple epithelial tissues and localizes to the apical and junctional actin cortex in intestinal and kidney epithelial cells. SMTNL2 deficiency leads to membrane herniations in the apical domain of epithelial cells, indicative of cortex abnormalities. We find that SMTNL2 binds to actin filaments and is required to slow down the turnover of apical actin. We also characterize the SMTNL2 proximal interactome and find that SMTNL2 executes its functions partly through inhibition of coronin-1B. Although coronin-1B-mediated actin dynamics are required for early morphogenesis, its sustained activity is detrimental for the mature apical shape. SMTNL2 binds to coronin-1B through its N-terminal coiled-coil region and negates its function to stabilize the apical cortex. In sum, our results unveil a mechanism for regulating actin dynamics during epithelial morphogenesis, providing critical insights on the developmental control of the cellular cortex.

SUBMITTER: Hachimi M

PROVIDER: S-EPMC8157312 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Development and homeostasis of blood vessels critically depend on the regulation of endothelial cell-cell junctions. Perturbations in cell-cell junction organization and function results in developmental defects and vascular pathologies including chronic inflammation, edema and atherosclerosis. Although many aspects of blood vessel formation and homeostasis depend on cell-cell junctions, the molecular mechanisms that regulate their dynamic rearrangement are not fully understood. The VEcad-catenin complex, which constitute the molecular basis of the adherens junctions (AJ), is connected to the actin cytoskeleton and its function is regulated by cytoskeletal contraction and actin-driven plasma membrane protrusions. Junction-associated intermitted lamellipodia (JAIL) are small actin-driven protrusions at cell-cell junctions controlled by the actin related protein 2/3 (Arp2/3)-complex that contribute to the regulation of cell-cell junctions. JAIL drive VEcad dynamics within the cell-cell junction thereby being critical for monolayer integrity, cell migration and angiogenesis. The molecular mechanisms regulating JAIL during vessel development are not completely understood. Coronin 1B (Coro1B) is an actin binding protein that controls actin networks at classical lamellipodia via both Arp2/3 complex and cofilin-mediated pathways. The role of Coro1B in endothelial cell (ECs) is not fully understood. In this study we demonstrate that Coro1B is a novel component and regulator of cell-cell junctions in ECs. Immunofluorescence studies show that Coro1B colocalizes with VEcad at cell-cell junctions in monolayers of ECs. Live-cell imaging reveal that Coro1B is recruited to, and operated at, actin-driven membrane protrusions at the cell-cell junctions. Coro1B recruitment to cell-cell junctions is regulated by cytoskeleton tension. By analyzing the Coro1B interactome, we identify integrin linked kinase (ILK) as new Coro1B-associated protein. Coro1B colocalizes with α-parvin, an interactor of ILK, at the leading edge of lamellipodia protrusions. Finally, functional experiments reveal that depletion of Coro1B causes defects in actin cytoskeleton and cell-cell junctions. In matrigel vessel network assays, depletion of Coro1B results in reduced network complexity, vessel number and vessel length. Together, our findings point towards a critical role for Coro1B in the dynamic remodeling of endothelial cell-cell junction and the assembly of vessel network.

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Smoothelin-like 2 Inhibits Coronin-1B to Stabilize the Apical Actin Cortex during Epithelial Morphogenesis.

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