PKCζ regulates Notch receptor routing and activity in a Notch signaling-dependent manner

Abstract

Activation of Notch signaling requires intracellular routing of the receptor, but the mechanisms controlling the distinct steps in the routing process is poorly understood. We identify PKCζ as a key regulator of Notch receptor intracellular routing. When PKCζ was inhibited in the developing chick central nervous system and in cultured myoblasts, Notch-stimulated cells were allowed to undergo differentiation. PKCζ phosphorylates membrane-tethered forms of Notch and regulates two distinct routing steps, depending on the Notch activation state. When Notch is activated, PKCζ promotes re-localization of Notch from late endosomes to the nucleus and enhances production of the Notch intracellular domain, which leads to increased Notch activity. In the non-activated state, PKCζ instead facilitates Notch receptor internalization, accompanied with increased ubiquitylation and interaction with the endosomal sorting protein Hrs. Collectively, these data identify PKCζ as a key regulator of Notch trafficking and demonstrate that distinct steps in intracellular routing are differentially modulated depending on Notch signaling status.

The Scribble–Dlg–Lgl Module in Cell Polarity Regulation

“…Interestingly, this role for Lgl in Notch signaling in Drosophila is aPKC independent. This contrasts studies in vertebrates, where a role for aPKC in regulating Notch receptor intracellular trafficking has been revealed in the chick central nervous system in vivo and myogenic precursors in vitro (Sjoqvist et al 2014). In this study aPKC (PKCζ) was shown to phosphorylate the Notch1 receptor on Serine-1791, which promoted trafficking of ligand-activated Notch to the nucleus thereby promoting signaling.…”

Selective regulation of Notch ligands during angiogenesis is mediated by vimentin

“…Vimentin interacts with membrane-tethered proteins through PDZ motifs (48) and Jagged and Dll carry distinct PDZ sequences in their ICDs (49)(50)(51). Whereas the ECDs are important for receptor binding, the ICDs play important roles in signal activation through posttranslational modifications (37,52) and interactions with endocytic regulators (41)(42)(43). To elucidate whether the ICDs of Dll4 and Jagged 1 influence vimentin binding and Notch signaling, we swapped the ICDs of Dll4 and Jagged 1 (53) to generate the chimeric variants: JaggedECDDll4ICD and Dll4ECDJaggedICD.…”

“…by protein trafficking (41)(42)(43). In addition to controlling number of ligands and receptors on the cell surface, ligand endocytosis is required for receptor activation (41).…”

Regulation of Notch signaling and endocytosis by the Lgl neoplastic tumor suppressor

“…Whether aPKC is involved here was not investigated, however, in the chick central nervous system and myogenic precursors, an aPKC-dependent mechanism controls Notch signalling. 79 In these cells, aPKCz regulates ligand-dependent Notch1 signalling via phosphorylation of the Notch1 receptor on Ser-1791, which promotes trafficking of ligandactivated Notch1 to the nucleus, where it activates target gene expression. In the absence of ligand, aPKC instead promotes Notch1 internalization from the cell surface and from the secretory golgi-ER pathway to intracellular vesicles, where it is inactive.…”

“…Similarly in vertebrates, from limited information currently available, Lgl and aPKC have been shown to regulate Notch signalling via different mechanisms in different systems. 78,79 During mouse brain development, the Lgl ortholog, Llgl1, is involved in the differentiation of neuroprogenitor cells. 78 These Llgl1 mutant neuro-progenitor cells fail to exit the cell cycle and differentiate, which is associated with the failure to segregate Numb and inhibit Notch signalling in the progenitor cells.…”