Establishment of the PAR-1 cortical gradient by the aPKC-PRBH circuit


Cell polarity is the asymmetric compartmentalization of cellular components. An opposing gradient of partitioning-defective protein kinases, atypical protein kinase C (aPKC) and PAR-1, at the cell cortex guides diverse asymmetries in the structure of metazoan cells, but the mechanism underlying their spatial patterning remains poorly understood. Here, we show in Caenorhabditis elegans zygotes that the cortical PAR-1 gradient is patterned as a consequence of dual mechanisms: stabilization of cortical dynamics and protection from aPKC-mediated cortical exclusion. Dual control of cortical PAR-1 depends on a physical interaction with the PRBH-domain protein PAR-2. Using a reconstitution approach in heterologous cells, we demonstrate that PAR-1, PAR-2, and polarized Cdc42-PAR-6-aPKC comprise the minimal network sufficient for the establishment of an opposing cortical gradient. Our findings delineate the mechanism governing cortical polarity, in which a circuit consisting of aPKC and the PRBH-domain protein ensures the local recruitment of PAR-1 to a well-defined cortical compartment.

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Fig. 1: Cortical localization of PAR-1 is tightly associated with cortical PAR-2.
Fig. 2: Cortical PAR-1 localization relies on interactions with phospholipids and PAR-2, and is antagonized by PKC-3.
Fig. 3: PAR-2 stimulates cortical localization of PAR-1 by inhibiting the activity of PKC-3 on PAR-1.
Fig. 4: PAR-2 stimulates cortical localization of PAR-1 by stabilizing its cortical dynamics.
Fig. 5: The PAR-1 cortical localization is essential for efficient segregation of P-granules.
Fig. 6: Polarized PKC-3 and PAR-2 are sufficient for the establishment of cortical PAR-1 gradient.


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This study was supported by the Singapore National Research Foundation (NRF) to F.M. (NRF-NRFF-2012-08) and to P.K. (NRF-NRFF-2011-04); by the Ministry of Education AcRF Tier 2 to P.K. (MOE-T2-1-045 and MOE-T2-1-124); and by the Strategic Japan-Singapore Cooperative Research Program by the Japan Science and Technology Agency and the Singapore Agency for Science, Technology, and Research to F.M. (1514324022). We thank J. Ahringer (University of Cambridge); E. Bi and H. Okada (University of Pennsylvania); N. Goehring (The Francis Crick Institute); P. Gonczy (EPFL); M. Gotta (Université de Genève); K. Kemphues (Cornell University); W. Lim (UCSF); A. Schwager, C. Hoege and A. Hyman (MPI); S. Mathew, D. Ng, and D. Zhang (TLL, Singapore); G. Seydoux (Johns Hopkins University); T. Wohland, S. Yavas, A. Yuan and M. Xiaobing (NUS, Singapore); and the Caenorhabditis Genetic Center for strains, reagents and expertise. We also thank R. Zaidel-Bar and A. Wong (MBI, Singapore), E.E. Griffin (Dartmouth College), and members of the Motegi lab for helpful comments on the manuscript.

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The experimental design and presented ideas were developed together by all authors. F.M. guided the study and wrote the manuscript with input from all authors. Z.H. performed experiments in Fig. 6 and Supplementary Fig. 6. F.M. performed experiments in Fig. 3d,e. R.R. performed all other experiments. Z.Z. and P.K. developed program codes for cortical intensity analysis in Fig. 1c–j.

Correspondence to Fumio Motegi.

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Ramanujam, R., Han, Z., Zhang, Z. et al. Establishment of the PAR-1 cortical gradient by the aPKC-PRBH circuit. Nat Chem Biol 14, 917–927 (2018).

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