A non-linear system patterns Rab5 GTPase on the membrane.

Alice Cezanne,Ivo F Sbalzarini,Janelle Lauer,Marino Zerial,Anastasia Solomatina

doi:10.7554/elife.54434

Abstract

Proteins can self-organize into spatial patterns via non-linear dynamic interactions on cellular membranes. Modelling and simulations have shown that small GTPases can generate patterns by coupling guanine nucleotide exchange factors (GEF) to effectors, generating a positive feedback of GTPase activation and membrane recruitment. Here, we reconstituted the patterning of the small GTPase Rab5 and its GEF/effector complex Rabex5/Rabaptin5 on supported lipid bilayers. We demonstrate a 'handover' of Rab5 from Rabex5 to Rabaptin5 upon nucleotide exchange. A minimal system consisting of Rab5, RabGDI and a complex of full length Rabex5/Rabaptin5 was necessary to pattern Rab5 into membrane domains. Rab5 patterning required a lipid membrane composition mimicking that of early endosomes, with PI(3)P enhancing membrane recruitment of Rab5 and acyl chain packing being critical for domain formation. The prevalence of GEF/effector coupling in nature suggests a possible universal system for small GTPase patterning involving both protein and lipid interactions.

Highlights

Membrane compartmentalization is of central importance for a variety of biological functions at multiple scales, from sub-cellular structures to multi-cellular organisms
To directly test the positive feedback loop model, we investigated the structural rearrangements occurring in Rab[5] and Rabex5/Rabaptin[5] in the course of nucleotide exchange by Hydrogen
guanine nucleotide exchange factors (GEF)/effector coupling and the resulting positive feedback loop of GTPase activation and membrane recruitment are common to many small GTPase systems and have been implicated in their spatial patterning

Summary

Introduction

Membrane compartmentalization is of central importance for a variety of biological functions at multiple scales, from sub-cellular structures to multi-cellular organisms. Processes such as cell polarization, protein and lipid sorting within sub-cellular organelles or cell and tissue morphogenesis depend on the emergence of patterns (Turing, 1952; Halatek et al, 2018). In Caenorhabditis elegans, symmetry breaking of the plasma membrane is caused by PAR proteins that sort into distinct anterior and posterior cortical domains and generate cell polarity (Kemphues et al, 1988, Motegi & Seydoux, 2013). ROP11 is organized into multiple domains on the PM where it interacts with cortical microtubules to regulate cell wall architecture (Yang and Lavagi 2012; Oda and Fukuda 2012). On early endosomes (EE), Rab[5] exists in domains where it regulates vesicle tethering and fusion (McBride et al 1999; Sönnichsen et al 2000; Franke et al 2019)

Methods

Results

Conclusion