The phospholipase A₂ enzyme complex PAFAH Ib mediates endosomal membrane tubule formation and trafficking.

Previous studies have shown that membrane tubule-mediated export from endosomal compartments requires a cytoplasmic phospholipase A(2) (PLA(2)) activity. Here we report that the cytoplasmic PLA(2) enzyme complex platelet-activating factor acetylhydrolase (PAFAH) Ib, which consists of α1, α2, and LIS1 subunits, regulates the distribution and function of endosomes. The catalytic subunits α1 and α2 are located on early-sorting endosomes and the central endocytic recycling compartment (ERC) and their overexpression, but not overexpression of their catalytically inactive counterparts, induced endosome membrane tubules.

ESCRT-II coordinates the assembly of ESCRT-III filaments for cargo sorting and multivesicular body vesicle formation.

The sequential action of five distinct endosomal-sorting complex required for transport (ESCRT) complexes is required for the lysosomal downregulation of cell surface receptors through the multivesicular body (MVB) pathway. On endosomes, the assembly of ESCRT-III is a highly ordered process. We show that the length of ESCRT-III (Snf7) oligomers controls the size of MVB vesicles and addresses how ESCRT-II regulates ESCRT-III assembly.

Assembly of an intact Golgi complex requires phospholipase A2 (PLA2) activity, membrane tubules, and dynein-mediated microtubule transport.

Previous studies have shown that treatment of mammalian cells with phospholipase A(2) (PLA(2)) antagonists cause the normally interconnected Golgi ribbon to break up into large fragments of stacked Golgi cisternae ("mini-stacks") that remain located in the juxtanuclear region. Using the reversible PLA(2) antagonist, ONO-RS-082 (ONO) and live-cell, time-lapse microscopy to image the Golgi reassembly process, we found that Golgi mini-stacks underwent a burst of membrane tubule formation following washout of ONO: before washout only 4.3+/-3.

Molecular mechanism of membrane constriction and tubulation mediated by the F-BAR protein Pacsin/Syndapin.

Peripheral membrane proteins of the Bin/amphiphysin/Rvs (BAR) and Fer-CIP4 homology-BAR (F-BAR) family participate in cellular membrane trafficking and have been shown to generate membrane tubules. The degree of membrane bending appears to be encoded in the structure and immanent curvature of the particular protein domains, with BAR and F-BAR domains inducing high- and low-curvature tubules, respectively. In addition, oligomerization and the formation of ordered arrays influences tubule stabilization.

The lysophospholipid acyltransferase antagonist CI-976 inhibits a late step in COPII vesicle budding.

The mechanism of coat protein (COP)II vesicle fission from the endoplasmic reticulum (ER) remains unclear. Lysophospholipid acyltransferases (LPATs) catalyze the conversion of various lysophospholipids to phospholipids, a process that can promote spontaneous changes in membrane curvature. Here, we show that 2,2-methyl-N-(2,4,6,-trimethoxyphenyl)dodecanamide (CI-976), a potent LPAT inhibitor, reversibly inhibited export from the ER in vivo and the formation of COPII vesicles in vitro.