From molecular structure to pattern formation – how to regulate a cell polarity kinase in time and space

A Crick PhD position for the 2021 programme in the labs of Neil McDonald and Nate Goehring.

Project background and description

The vast majority of cells are functionally polarized along at least one geometric axis, which enables them to migrate across developing embryos, establish complex morphologies within tissues, and divide asymmetrically to yield daughter cells with distinct fates. Loss of polarity can severely impact cell fate specification, proliferation control and self-renewal during stem-cell like divisions, epithelial to mesenchymal transitions, and metastasis. Mutations in polarity-related molecules are linked to cancer and active programmes are in place to develop therapeutics based on manipulating the polarity-related pathways.

In animal cells, a central player in cell polarisation is the polarity kinase atypical protein kinase C (aPKC), which is responsible for the spatial regulation of numerous pathways. In particular, its ability to modify the membrane association of various substrates enables the generation of asymmetric and distinct functional membrane domains that define the polarity of the cell. Yet despite its fundamental role in polarising cells, we are only beginning to understand how this kinase is regulated in time and space or how it selectively targets diverse polarity substrates.

Work from our labs has shown that aPKC function is tightly linked to its ability to form dynamic complexes with other polarity proteins, including scaffolding proteins Par6, Par3 and the small GTPase Cdc42, which can modulate both its membrane targeting, its overall localisation, and kinase activity [1,2]. We have also developed new tools to manipulate aPKC in live cells [1,3] and identified docking motifs that modulate substrate recognition [4,5]. Recent work suggests that distinct multi-component PAR complexes show highly specific patterns of substrate selectivity.  The key next step will be to develop multi-scale analysis methods to link detailed molecular behaviour described in vitro to system-level quantitative readouts of PAR protein behaviour in polarised cells, and ultimately to disease- and development-relevant phenotypes.

Through this multi-disciplinary project, we aim to develop a toolkit to identify key states of the PAR complex and define their impact on cell polarity.  While the precise project will be decided in consultation with and tailored to the interests and skillset of the candidate, a key aspect will be to foster reciprocal connections between structural and biochemical insights and in vivo biological readouts, with the ultimate aim of defining core design principles of the PAR polarity network.  To this end, we expect the candidate will work closely with teams in both labs who are exploring cell polarity pathways via a variety of techniques, including cryo-EM and crystallography, in vitro biochemistry, mass spectrometry, quantitative live cell imaging, genetics and genome engineering, and mathematical modelling.  Examples of projects could include design of biosensors, understanding the role of kinase-substrate binding motifs in PAR network behavior, structural exploration of PAR complex intermediates, and/or in vitro reconstitution of cell polarity pathways. 

Candidate background

The ideal candidate will have a strong interest in bridging fields of biomedical research and be comfortable working across the spectrum of biological scales.  We expect candidates to have a degree and/or background in biochemistry or similar with experience in structural and/or cell biology.  Due to the joint nature of the post, an open, collaborative, and highly self-motivated personality is essential.

References

 

1.       Rodriguez, J., Peglion, F., Martin, J., Hubatsch, L., Reich, J., Hirani, N., . . . Goehring, N.W. (2017)

          aPKC cycles between functionally distinct PAR protein assemblies to drive cell polarity.

          Developmental Cell 42: 400-415. PubMed abstract

2.       Reich, J.D., Hubatsch, L., Illukkumbura, R., Peglion, F., Bland, T., Hirani, N. and Goehring, N.W. (2019)

          Regulated activation of the PAR polarity network ensures a timely and specific response to spatial cues.

          Current Biology 29: 1911-1923.e1915. PubMed abstract

3.       Kjær, S., Linch, M., Purkiss, A., Kostelecky, B., Knowles, P.P., Rosse, C., . . . McDonald, N.Q. (2013)

          Adenosine-binding motif mimicry and cellular effects of a thieno[2,3-d]pyrimidine-based chemical inhibitor of atypical protein kinase C isoenzymes.

          Biochemical Journal 451: 329-342. PubMed abstract

4.       Linch, M., Sanz-Garcia, M., Soriano, E., Zhang, Y., Riou, P., Rosse, C., . . . Parker, P.J. (2013)

          A cancer-associated mutation in atypical protein kinase Cι occurs in a substrate-specific recruitment motif.

          Science Signaling 6: ra82. PubMed abstract

5.       Soriano, E.V., Ivanova, M.E., Fletcher, G., Riou, P., Knowles, P.P., Barnouin, K., . . . McDonald, N.Q. (2016)

          aPKC inhibition by Par3 CR3 flanking regions controls substrate access and underpins apical-junctional polarization.

          Developmental Cell 38: 384-398. PubMed abstract