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Published on: September 28, 2018
Control of atypical PKCι membrane dissociation by tyrosine phosphorylation within a PB1-C1 interdomain interface
Mathias Cobbaut1, Neil Q McDonald2, Peter J Parker3
1Signalling and Structural Biology Laboratory, The Francis Crick Institute, London, UK; Protein Phosphorylation Laboratory, The Francis Crick Institute, London, UK.
Abstract:
Atypical PKCs are cell polarity kinases that operate at the plasma membrane where they function within multiple molecular complexes to contribute to the establishment and maintenance of polarity. In contrast to the classical and novel PKCs, atypical PKCs do not respond to diacylglycerol cues to bind the membrane compartment. Until recently, it was not clear how aPKCs are recruited; whether aPKCs can directly interact with membranes or whether they are dependent on other protein interactors to do so. Two recent studies identified the pseudosubstrate region and the C1 domain as direct membrane interaction modules; however, their relative importance and coupling are unknown. We combined molecular modeling and functional assays to show that the regulatory module of aPKCι, comprising the PB1 pseudosubstrate and C1 domains, forms a cooperative and spatially continuous invariant membrane interaction platform. Furthermore, we show the coordinated orientation of membrane-binding elements within the regulatory module requires a key PB1-C1 interfacial β-strand (beta-strand linker). We show this element contains a highly conserved Tyr residue that can be phosphorylated and that negatively regulates the integrity of the regulatory module, leading to membrane release. We thus expose a hitherto unknown regulatory mechanism of aPKCι membrane binding and release during cell polarization.
Insights
Atypical protein kinase Cs (aPKCs) use a regulatory module for membrane binding during cell polarization. Phosphorylation of a key residue in this module controls aPKC binding and release, revealing a novel regulatory mechanism.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Atypical protein kinase Cs (aPKCs) are crucial for establishing and maintaining cell polarity at the plasma membrane.
- Unlike other PKC types, aPKCs do not rely on diacylglycerol for membrane recruitment, and their precise membrane interaction mechanisms were unclear.
Purpose of the Study:
- To investigate how atypical PKCs (aPKCs) are recruited to the plasma membrane.
- To elucidate the role of the pseudosubstrate and C1 domains in aPKC membrane binding.
- To identify the regulatory mechanisms governing aPKC membrane association and dissociation.
Main Methods:
- Utilized molecular modeling to analyze the regulatory module of aPKCι.
- Employed functional assays to validate computational findings.
- Investigated the role of a specific beta-strand linker and tyrosine phosphorylation.
Main Results:
- The pseudosubstrate (PB1) and C1 domains of aPKCι form a cooperative membrane interaction platform.
- A conserved tyrosine residue within the PB1-C1 linker is critical for maintaining the regulatory module's integrity.
- Phosphorylation of this tyrosine residue negatively regulates the module, leading to aPKCι release from the membrane.
Conclusions:
- A novel regulatory mechanism for aPKCι membrane binding and release has been identified.
- The integrity of the aPKCι regulatory module is controlled by phosphorylation of a key tyrosine residue.
- This mechanism provides new insights into the dynamic regulation of cell polarity.
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