The interaction between CASK and the tumour suppressor Dlg1 regulates mitotic spindle orientation in mammalian epithelia.

Andrew P Porter,Natalie A Mack,Angeliki Malliri,Gavin R M White

doi:10.1242/jcs.230086

Andrew P Porter, Natalie A Mack + Show 2 more

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https://doi.org/10.1242/jcs.230086

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Abstract

ABSTRACTOriented cell divisions are important for the formation of normal epithelial structures. Dlg1, a tumour suppressor, is required for mitotic spindle orientation in Drosophila epithelia and chick neuroepithelia, but how Dlg1 is localised to the membrane and its importance in mammalian epithelia are unknown. We show that Dlg1 is required in non-transformed mammalian epithelial cells for oriented cell divisions and normal lumen formation. We demonstrate that the MAGUK protein CASK, a membrane-associated scaffold, is the factor responsible for Dlg1 membrane localisation during spindle orientation, thereby identifying a new cellular function for CASK. Depletion of CASK leads to misoriented divisions in 3D, and to the formation of multilumen structures in cultured kidney and breast epithelial cells. Blocking the CASK–Dlg1 interaction with an interfering peptide, or by deletion of the CASK-interaction domain of Dlg1, disrupts spindle orientation and causes multilumen formation. We show that the CASK–Dlg1 interaction is important for localisation of the canonical LGN–NuMA complex known to be required for spindle orientation. These results establish the importance of the CASK–Dlg1 interaction in oriented cell division and epithelial integrity.This article has an associated First Person interview with the first author of the paper.

Highlights

Control of the orientation of cell division – via correct positioning of the mitotic spindle – plays an important role in developing and maintaining tissue architecture in both embryonic and adult tissues (Bergstralh et al, 2017)
In this report we show that discs large homolog 1 (Dlg1) is required for spindle orientation in 3D cultures of untransformed mammalian epithelial cells, and identify the membrane-associated guanylate kinase (MAGUK) protein CASK as the protein responsible for Dlg1 membrane localisation in the context of spindle orientation
Dlg1 regulates spindle orientation and epithelial lumen formation in mammalian cells MDCKII cells seeded onto Matrigel have the capacity to grow as cysts, reminiscent of those found in the mammalian kidney, with a hollow lumen surrounded by a single layer of epithelial cells

Summary

Introduction

Control of the orientation of cell division – via correct positioning of the mitotic spindle – plays an important role in developing and maintaining tissue architecture in both embryonic and adult tissues (Bergstralh et al, 2017). Epithelial cells tend to divide in the plane of the epithelium, which is important to integrate daughter cells within the epithelium and thereby maintain barrier function (Bergstralh et al, 2013a). These oriented divisions are hypothesised to have a tumoursuppressive function (Pease and Tirnauer, 2011), direct evidence of its importance for tumourigenesis is limited at this point

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