Excess vacuolar SNAREs drive lysis and Rab bypass fusion

jiangyun submitted, created time 1 year 4 months (www.pnas.org)

Although concentrated soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) drive liposome fusion and lysis, the fusion of intracellular membranes also requires Rab GTPases, Rab effectors, SM proteins, and specific regulatory lipids and is accompanied by little or no lysis. To rationalize these findings, we generated yeast strains that overexpress all four vacuolar SNAREs (4SNARE++)

Submit comment | Blog It | Email It | Keywords: homotypic fusion and vacuole protein sor membrane fusion Rab GTPase yeast vacuoles

XRab40 and XCullin5 form a ubiquitin ligase complex essential for the noncanonical Wnt pathway

bioman submitted, created time 1 year 5 months (www.nature.com)

Rab GTPases are key regulators of intracellular membrane trafficking. We sought to elucidate the roles of Rab GTPases in Xenopus gastrulation, and found that a Xenopus homolog of Rab40 (XRab40) is required for normal gastrulation. XRab40 is localized at the Golgi apparatus and interacts with ElonginB/C and Cullin5 to form a ubiquitin ligase. XRab40/XCullin5 functions cooperatively and regulates the ubiquitination and localization of Rap2 GTPase

Submit comment | Blog It | Email It | Keywords: gastrulation Rab GTPase ubiquitination Wnt signaling Xenopus

Structural basis for Rab GTPase activation by VPS9 domain exchange factors

claudia submitted, created time 1 year 8 months (www.nature.com)

RABEX-5 and other exchange factors with VPS9 domains regulate endocytic trafficking through activation of the Rab family GTPases RAB5, RAB21 and RAB22. The scientists here report the crystal structure of the RABEX-5 catalytic core in complex with nucleotide-free RAB21, a key intermediate in the exchange reaction pathway. The structure reveals how VPS9 domain exchange factors recognize Rab GTPase substrates, accelerate GDP release and stabilize the nucleotide-free conformation.

Submit comment | Blog It | Email It | Keywords: Rab GTPase VPS9 domain