TY - JOUR
T1 - Atypical PKC phosphorylates PAR-1 kinases to regulate localization and activity
AU - Hurov, Jonathan B.
AU - Watkins, Janis L.
AU - Piwnica-Worms, Helen
N1 - Funding Information:
In this study we identified a novel phosphorylation site that regulates the activity and intracellular compartmentalization of the human Par-1b kinase. We demonstrate that hPar-1b is phosphorylated on T595 in vivo and that in nonpolarized cells, phosphorylation of hPar-1b on T595 negatively regulates plasma membrane association and kinase activity of hPar-1b. Our findings that aPKC associates with hPar-1b in vivo, that ectopic expression of aPKC results in enhanced phosphorylation of hPar-1b on T595 in vivo, and that aPKC phosphorylates hPar-1 on T595 in vitro suggest that hPar-1b is a physiological substrate of aPKC in vivo. Interestingly, the other mammalian Par-1 kinases, as well as orthologs in C. elegans and Drosophila , conserve a threonine residue in the equivalent position to T595. In the case of hPar-1a, we show that T564 is phosphorylated in vivo and that PKCζ phosphorylates hPar-1a on T564 in vitro. Thus, the regulation of Par-1 by aPKC may be a conserved regulatory pathway throughout evolution. Our observation that aPKC regulates Par-1 localization in vivo is supported by the observation that in C. elegans Par-1 localization is perturbed by Par-3/Par-6/aPKC mutation [19, 20] . This model of regulation of Par-1 localization by aPKC is reminiscent of the finding that Lgl localization is also regulated in a phosphorylation-dependent manner by aPKC [21–23] . We have not ruled out the possibility that Par-1 reciprocally regulates aPKC, since the localization of PKCζ to the plasma membrane appears to be at least partially dependent on hPar-1b.
PY - 2004/4/20
Y1 - 2004/4/20
N2 - The establishment and maintenance of cellular polarity are essential biological processes that must be maintained throughout the lifetime of eukaryotic organisms. The Par-1 protein kinases are key polarity determinants that have been conserved throughout evolution. Par-1 directs anterior-posterior asymmetry in the one-cell C. elegans embryo and the Drosophila oocyte [1]. In mammalian cells, Par-1 may regulate epithelial cell polarity [2]. Relevant substrates of Par-1 in these pathways are just being identified, but it is not yet known how Par-1 itself is regulated. Here, we demonstrate that human Par-1b (hPar-1b) interacts with and is negatively regulated by atypical PKC. hPar-1b is phosphorylated by aPKC on threonine 595, a residue conserved in Par-1 orthologs in mammals, worms, and flies. The equivalent site in hPar-1a, T564, is phosphorylated in vivo and by aPKC in vitro. Importantly, phosphorylation of hPar-1b on T595 negatively regulates the kinase activity and plasma membrane localization of hPar-1b in vivo. This study establishes a novel functional link between two central determinants of cellular polarity, aPKC and Par-1, and suggests a model by which aPKC may regulate Par-1 in polarized cells.
AB - The establishment and maintenance of cellular polarity are essential biological processes that must be maintained throughout the lifetime of eukaryotic organisms. The Par-1 protein kinases are key polarity determinants that have been conserved throughout evolution. Par-1 directs anterior-posterior asymmetry in the one-cell C. elegans embryo and the Drosophila oocyte [1]. In mammalian cells, Par-1 may regulate epithelial cell polarity [2]. Relevant substrates of Par-1 in these pathways are just being identified, but it is not yet known how Par-1 itself is regulated. Here, we demonstrate that human Par-1b (hPar-1b) interacts with and is negatively regulated by atypical PKC. hPar-1b is phosphorylated by aPKC on threonine 595, a residue conserved in Par-1 orthologs in mammals, worms, and flies. The equivalent site in hPar-1a, T564, is phosphorylated in vivo and by aPKC in vitro. Importantly, phosphorylation of hPar-1b on T595 negatively regulates the kinase activity and plasma membrane localization of hPar-1b in vivo. This study establishes a novel functional link between two central determinants of cellular polarity, aPKC and Par-1, and suggests a model by which aPKC may regulate Par-1 in polarized cells.
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U2 - 10.1016/j.cub.2004.04.007
DO - 10.1016/j.cub.2004.04.007
M3 - Article
C2 - 15084291
AN - SCOPUS:1942540791
SN - 0960-9822
VL - 14
SP - 736
EP - 741
JO - Current Biology
JF - Current Biology
IS - 8
ER -