Abstract
Atypical protein kinase C (aPKC) controls cell polarity by modulating substrate cortical localization. Aberrant aPKC activity disrupts polarity, yet the mechanisms that control aPKC remain poorly understood. We used a reconstituted system with purified components and a cultured cell cortical displacement assay to investigate aPKC regulation. We find that aPKC is autoinhibited by two domains within its NH(2)-terminal regulatory half, a pseudosubstrate motif that occupies the kinase active site, and a C1 domain that assists in this process. The Par complex member Par-6, previously thought to inhibit aPKC, is a potent activator of aPKC in our assays. Par-6 and aPKC interact via PB1 domain heterodimerization, and this interaction activates aPKC by displacing the pseudosubstrate, although full activity requires the Par-6 CRIB-PDZ domains. We propose that, along with its previously described roles in controlling aPKC localization, Par-6 allosterically activates aPKC to allow for high spatial and temporal control of substrate phosphorylation and polarization.
Highlights
Many cell polarities are controlled by the Par complex, which includes Par-6 and atypical protein kinase C
APKC activity is required for many cell polarities, excess activity can lead to tissue disorganization and overproliferation
A central question in cell polarity is how atypical protein kinase C (aPKC) catalytic activity is kept in an appropriate range during dynamic processes such as asymmetric cell division
Summary
Many cell polarities are controlled by the Par complex, which includes Par-6 and atypical protein kinase C (aPKC). Atypical protein kinase C (aPKC) controls cell polarity by modulating substrate cortical localization. We investigate Par complex regulation by determining the molecular mechanisms by which aPKC activity is controlled. In Drosophila neuroblasts the protein Miranda localizes to a cortical domain opposite the Par complex, and its polarization requires aPKC activity [8]. All PKC isoforms contain NH2-terminal domains that are potentially important for controlling the activity of the COOH-terminal kinase domain [19] These domains include the aPKC-specific PB1 that binds Par-6 [18] and the C1 domain that binds lipid cofactors such as diacylglycerol in other PKC family members [20, 21], but whose function in aPKCs is unknown [22]. We explore the interplay between internal aPKC regulatory elements and the protein-protein interactions that are thought to control aPKC activity during cell polarization
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
