Nup358 regulates microridge length by controlling SUMOylation-dependent activity of aPKC in zebrafish epidermis

The Par polarity complex, consisting of Par3, Par6 and atypical protein kinase C (aPKC), plays a crucial role in the establishment and maintenance of cell polarity. Although activation of aPKC is critical for polarity, how this is achieved is unclear. The developing zebrafish epidermis, along with its apical actin-based projections, called microridges, offers a genetically tractable system for unraveling the mechanisms of the cell polarity control. The zebrafish aPKC regulates elongation of microridges by controlling levels of apical Lgl, which acts as a pro-elongation factor. Here, we show that the nucleoporin Nup358 (also known as RanBP2) - a component of the nuclear pore complex and a part of cytoplasmic annulate lamellae (AL) - SUMOylates zebrafish aPKC. Nup358-mediated SUMOylation controls aPKC activity to regulate Lgl-dependent microridge elongation. Our data further suggest that cytoplasmic AL structures are the possible site for Nup358-mediated aPKC SUMOylation. We have unraveled a hitherto unappreciated contribution of Nup358-mediated aPKC SUMOylation in cell polarity regulation.This article has an associated First Person interview with the first author of the paper.