Phospholipase Cβ1 induces membrane tubulation and is involved in caveolae formation

Abstract

Lipid membrane curvature plays important roles in various physiological phenomena. Curvature-regulated dynamic membrane remodeling is achieved by the interaction between lipids and proteins. So far, several membrane sensing/sculpting proteins, such as Bin/ amphiphysin/Rvs (BAR) proteins, are reported, but there remains the possibility of the existence of unidentified membrane-deforming proteins that have not been uncovered by sequence homology. To identify new lipid membrane deformation proteins, we applied liposome-based microscopic screening, using unbiased-darkfield microscopy. Using this method, we identified phospholipase Cβ1 (PLCβ1) as a new candidate. PLCβ1 is well characterized as an enzyme catalyzing the hydrolysis of phosphatidylinositol-4,5-bisphosphate (PIP 2 ). In addition to lipase activity, our results indicate that PLCβ1 possessed the ability of membrane tubulation. Lipase domains and inositol phospholipids binding the pleckstrin homology (PH) domain of PLCβ1 were not involved, but the C-terminal sequence was responsible for this tubulation activity. Computational modeling revealed that the C terminus displays the structural homology to the BAR domains, which is well known as a membrane sensing/sculpting domain. Overexpression of PLCβ1 caused plasma membrane tubulation, whereas knockdown of the protein reduced the number of caveolae and induced the evagination of caveolin-rich membrane domains. Taken together, our results suggest a new function of PLCβ1: plasma membrane remodeling, and in particular, caveolae formation.phospholipase Cβ1 | membrane tubulation | microscopy screening | caveolae | BAR-like domain

The Impact of Nonequilibrium Conditions in Lung Surfactant: Structure and Composition Gradients in Multilamellar Films

“…During the buildup of the film, lipids are transferred from vesicles to the oriented interfacial layer through fusion processes. It is a recurring observation for all systems investigated that the fusion of vesicles with the interfacial film is associated with the formation of tubular structures ( Figure 6 ) that have similarities to the myelination, 67 − 70 fingering, 62 , 71 and tubulation 72 − 74 phenomena, which have been previously described for other systems. The mesostructure of the tubules was determined by SAXS, showing a lamellar phase with identical repeat distance as the inner fully swollen layer of the multilamellar film but an orientation along the curling of the tubules ( Figure 6 ).…”

Caveolae provide a specialized membrane environment for respiratory syncytial virus assembly

“…This could potentially lead to caveolae flattening and the incorporation of the flattened caveolar protein coat and caveolar lipids into the growing viral envelope. RSV infection also alters the lipid composition of raft membranes ( Yeo et al, 2009 ), and specific phospholipid-modifying enzymes have been proposed to control caveolae formation ( Inaba et al, 2016 ). It is conceivable, therefore, that RSV-induced changes to the caveolar lipid profile contribute to the initiation of RSV filament assembly within caveolar membranes, and to their incorporation into the RSV envelope.…”

Formation of tubules and helical ribbons by ceramide phosphoethanolamine-containing membranes

“…The shape of lipid assemblies in suspension was observed by darkfield microscopy 39 . The darkfield microscope (Eclipse E600, Nikon, Japan) was equipped with two objectives (100x, N.A.…”