title: A catalytic role for Mod5 in the formation of the Tea1 cell polarity landmark.
abstract: Many systems regulating cell polarity involve stable landmarks defined by internal cues. In the rod-shaped fission yeast Schizosaccharomyces pombe, microtubules regulate polarized vegetative growth via a landmark involving the protein Tea1. Tea1 is delivered to cell tips as packets of molecules associated with growing microtubule ends and anchored at the plasma membrane via a mechanism involving interaction with the membrane protein Mod5. Tea1 and Mod5 are highly concentrated in clusters at cell tips in a mutually dependent manner, but how the Tea1-Mod5 interaction contributes mechanistically to generating a stable landmark is not understood. Here, we use live-cell imaging, FRAP, and computational modeling to dissect dynamics of the Tea1-Mod5 interaction. Surprisingly, we find that Tea1 and Mod5 exhibit distinctly different turnover rates at cell tips. Our data and modeling suggest that rather than acting simply as a Tea1 receptor or as a molecular "glue" to retain Tea1, Mod5 functions catalytically to stimulate incorporation of Tea1 into a stable tip-associated cluster network. The model also suggests an emergent self-focusing property of the Tea1-Mod5 cluster network, which can increase the fidelity of polarized growth.
authors.affiliation: Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, UK.
authors.forename: Claudia C
authors.initials: CC
authors.lastname: Bicho
authors.forename: David A
authors.initials: DA
authors.lastname: Kelly
authors.forename: Hilary A
authors.initials: HA
authors.lastname: Snaith
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Goryachev
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Sawin
mesh_terms: D016764:Cell Polarity / Q000502:physiology*; D003198:Computer Simulation; D036681:Fluorescence Recovery After Photobleaching; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012568:Schizosaccharomyces / Q000166:cytology* / Q000502:physiology; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D008869:Microtubule-Associated Proteins; D011993:Recombinant Fusion Proteins; D029702:Schizosaccharomyces pombe Proteins; C432671:Tea1 protein, S pombe; C474999:mod5 protein, S pombe