Stratum, a Homolog of the Human GEF Mss4, Partnered with Rab8, Controls the Basal Restriction of Basement Membrane Proteins in Epithelial Cells

Publication date: 21 February 2017
Source:Cell Reports, Volume 18, Issue 8
Author(s): Olivier Devergne, Gina H. Sun, Trudi Schüpbach
The basement membrane (BM), a sheet of extracellular matrix lining the basal side of epithelia, is essential for epithelial cell function and integrity, yet the mechanisms that control the basal restriction of BM proteins are poorly understood. In epithelial cells, a specialized pathway is dedicated to restrict the deposition of BM proteins basally. Here, we report the identification of a factor in this pathway, a homolog of the mammalian guanine nucleotide exchange factor (GEF) Mss4, which we have named Stratum. The loss of Stratum leads to the missecretion of BM proteins at the apical side of the cells, forming aberrant layers in close contact with the plasma membrane. We found that Rab8GTPase acts downstream of Stratum in this process. Altogether, our results uncover the importance of this GEF/Rab complex in specifically coordinating the basal restriction of BM proteins, a critical process for the establishment and maintenance of epithelial cell polarity.

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Teaser

The proper placement of the basement membrane at the basal side of epithelial cells is essential for cellular function. Devergne et al. show that Stratum, a homolog of the mammalian GEF Mss4/RabIF, and its downstream effector Rab8GTPase are essential for the basal sorting of BM proteins in polarized epithelial cells.


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