PT  - JOURNAL ARTICLE
AU  - Robert M. Gingras
AU  - Kyaw Myo Lwin
AU  - Abigail M. Miller
AU  - Anthony Bretscher
TI  - Yeast Rgd3 is a phospho-regulated F-BAR-containing RhoGAP involved in the regulation of Rho3 distribution and cell morphology
AID  - 10.1101/2020.05.04.077206
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.05.04.077206
4099  - http://biorxiv.org/content/early/2020/05/05/2020.05.04.077206.1.short
4100  - http://biorxiv.org/content/early/2020/05/05/2020.05.04.077206.1.full
AB  - Polarized growth requires the integration of polarity pathways with the delivery of exocytic vesicles for cell expansion and counterbalancing endocytic uptake. In budding yeast, the myosin-V Myo2 is aided by the kinesin-related protein Smy1 in carrying out the essential Sec4-dependent transport of secretory vesicles to sites of polarized growth. Over-expression suppressors of a conditional myo2 smy1 mutant identified a novel F-BAR-containing RhoGAP, Rgd3, that has activity primarily on Rho3, but also Cdc42. Internally tagged Rho3 is restricted to the plasma membrane in a gradient corresponding to cell polarity that is altered upon Rgd3 over-expression. Rgd3 itself is localized to dynamic polarized vesicles that, while distinct from constitutive secretory vesicles, are dependent on actin and Myo2 function. In vitro Rgd3 associates with liposomes in a PIP2-enhanced manner. Further, the Rgd3 C-terminal region contains several phosphorylatable residues within a reported SH3-binding motif. An unphosphorylated mimetic construct is active and highly polarized, while the phospho-mimetic form is not. Rgd3 is capable of activating Myo2, dependent on its phospho-state and Rgd3 overexpression rescues aberrant Rho3 localization and cell morphologies seen at the restrictive temperature in the myo2 smy1 mutant. We propose a model where Rgd3 functions to modulate and maintain Rho3 polarity during growth.Competing Interest StatementThe authors have declared no competing interest.