Molecular Characterization of Caveolin-induced Membrane Curvature

Ariotti, Nicholas; Rae, James; Leneva, Natalya; Ferguson, Charles; Loo, Dorothy; Okano, Satomi; Hill, Michelle M.; Walser, Piers J.; Collins, Brett M.; Parton, Robert G.

doi:10.1074/jbc.m115.644336

Cited by 96 publications

(141 citation statements)

References 56 publications

Supporting

Mentioning

127

Contrasting

Order By: Relevance

“…Finally, cryoEM tomography of caveolae in situ suggested that rather than being purely spherical, caveola bulbs possess inherent polygonal symmetries. Interestingly, identical polygonal symmetry is observed by cryoEM in a model system in which CAV1 alone drives formation of caveolalike vesicles in bacterial membranes (13). This finding strongly suggests that CAV1 is responsible for this polygonal architecture, rather than the peripheral cavin coat, although in mammalian cells both components are required to form a stable caveola.…”

supporting

confidence: 61%

See 1 more Smart Citation

Unraveling the architecture of caveolae

Parton

Collins

2016

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

The eukaryotic cell surface is composed of many distinct membrane domains that are formed by the cooperative interactions of different proteins and lipids. These domains are important for membrane trafficking and cell signaling and are modulated in turn by changes in the cell environment. Caveolae ("little caves") are ∼60-nm membrane invaginations ( Fig. 1) that are a dominant surface feature of many mammalian cells, including muscle fibers, endothelia, and adipocytes, where they play a role in membrane homeostasis, signaling, and cellular mechanoprotection. Formation of caveolae in vertebrate cells requires two distinct protein families: the membrane-embedded caveolins (CAV1-3) and the peripheral membrane cavins (Cavin1-4). Although the general morphology of caveolae has been known for decades, the atypical structures of the protein subunits has meant that progress has been slow with regards to the high-resolution studies of caveola architecture. By high-resolution scanning electron microscopy (EM) and frozen deepetch transmission EM, caveolae have been shown to be coated with striations (1, 2) or to possess spike-like structures (3), very different from other well-characterized vesicle coats, such as clathrin (4, 5). In PNAS, Stoeber et al. use a combination of biochemical dissection and EM to provide important insights into the underlying architecture of the caveola protein coat (6).The first protein component of caveolae to be identified and shown to be essential for caveola formation was CAV1 (7-9). Subsequently, it was found that both CAV2 and muscle-specific CAV3 homologs are also localized to caveolae. Caveolin proteins are ∼20 kDa and possess two membrane-inserted α-helices with cytoplasmic N-and C-terminal sequences. These proteins form oligomeric complexes at the plasma membrane that line the cytoplasmic leaflet of the invaginated caveola structures. Cavins, although equally important for caveola formation, were only identified in the past decade through proteomic and cellular studies from several groups. Cavins also possess a conserved and unique structural organization, in this case consisting of conserved N-and C-terminal α-helical domains (HR1 and HR2) interspersed by disordered linker sequences (DR1, DR2, DR3) (10). Although recent studies have begun to tease out the functions of these domains in membrane recruitment, remodeling, and protein-protein interactions, our understanding is still limited. For example, how do caveolin oligomers assemble within caveolae, and what drives cavin oligomerization and recruitment to caveolar domains at the cell surface?In their report, Stoeber et al. (6) propose a model for the arrangement of the caveolin and cavin proteins that begins to address some of the ongoing questions in the field. Affinity purification of Cavin1 expressed in HEK293 cells revealed the presence of heterogeneous particles with a mesh-like appearance by cryoEM and 3D electron tomography. These particles bound robustly to liposomes containing phosphatidylserine (PS) or phosphatidic acid, as...

show abstract

supporting

confidence: 61%

“…Studies by many laboratories in recent years are now beginning to bridge this gulf using approaches that include biochemical isolation, NMR spectroscopy, EM, and X-ray crystallography (6,10,(12)(13)(14)(15)(16)(17). A picture is now emerging of a vesicular structure that possesses much greater complexity than originally thought.…”

mentioning

confidence: 99%

Unraveling the architecture of caveolae

Parton

Collins

2016

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Analysis of the reconstituted Cavin1 vesicles indicated that the Cavin1 coat alone can cause such polygonal shapes. In this context it is interesting that, when expressed in bacteria in the absence of cavins, caveolin generates vesicles of similar size and shape (34,35). Thus, the polygonal shape of caveolae is probably favored, generated, and maintained by both caveolins and cavins.…”

Section: Discussionmentioning

confidence: 99%

Model for the architecture of caveolae based on a flexible, net-like assembly of Cavin1 and Caveolin discs

Stoeber

Schellenberger

Siebert

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

110

View full text Add to dashboard Cite

Caveolae are invaginated plasma membrane domains involved in mechanosensing, signaling, endocytosis, and membrane homeostasis. Oligomers of membrane-embedded caveolins and peripherally attached cavins form the caveolar coat whose structure has remained elusive. Here, purified Cavin1 60S complexes were analyzed structurally in solution and after liposome reconstitution by electron cryotomography. Cavin1 adopted a flexible, net-like protein mesh able to form polyhedral lattices on phosphatidylserine-containing vesicles. Mutating the two coiled-coil domains in Cavin1 revealed that they mediate distinct assembly steps during 60S complex formation. The organization of the cavin coat corresponded to a polyhedral nano-net held together by coiled-coil segments. Positive residues around the C-terminal coiled-coil domain were required for membrane binding. Purified caveolin 8S oligomers assumed discshaped arrangements of sizes that are consistent with the discs occupying the faces in the caveolar polyhedra. Polygonal caveolar membrane profiles were revealed in tomograms of native caveolae inside cells. We propose a model with a regular dodecahedron as structural basis for the caveolae architecture.caveolae | coat proteins | coat assembly | membrane organization | electron cryomicroscopy

show abstract

“…From a structural standpoint, Cav1 contains a hairpin loop structure, three palmitoylation sites, and a scaffolding domain that facilitates interaction with the PM (12). The scaffolding domain of Cav1 (amino acids 82-101) contains three cationic residues that bind to the negatively charged headgroups of PtdSer and PtdIns(4,5)P 2 via electrostatic interactions (13,14).These in vitro studies revealed that PtdIns(4,5)P 2 is the preferred ligand on a per mole basis.…”

Section: Edited By Dennis R Voelkermentioning

confidence: 99%

Phosphatidylserine dictates the assembly and dynamics of caveolae in the plasma membrane

Hirama

Das

Yang

et al. 2017

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

Edited by Dennis R. VoelkerCaveolae are bulb-shaped nanodomains of the plasma membrane that are enriched in cholesterol and sphingolipids. They have many physiological functions, including endocytic transport, mechanosensing, and regulation of membrane and lipid transport. Caveola formation relies on integral membrane proteins termed caveolins (Cavs) and the cavin family of peripheral proteins. Both protein families bind anionic phospholipids, but the precise roles of these lipids are unknown. Here, we studied the effects of phosphatidylserine (PtdSer), phosphatidylinositol 4-phosphate (PtdIns4P), and phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P 2 ) on caveolar formation and dynamics. Using live-cell, single-particle tracking of GFP-labeled Cav1 and ultrastructural analyses, we compared the effect of PtdSer disruption or phosphoinositide depletion with caveola disassembly caused by cavin1 loss. We found that PtdSer plays a crucial role in both caveola formation and stability. Sequestration or depletion of PtdSer decreased the number of detectable Cav1-GFP puncta and the number of caveolae visualized by electron microscopy. Under PtdSer-limiting conditions, the co-localization of Cav1 and cavin1 was diminished, and cavin1 degradation was increased. Using rapamycin-recruitable phosphatases, we also found that the acute depletion of PtdIns4P and PtdIns (4,5)P 2 has minimal impact on caveola assembly but results in decreased lateral confinement. Finally, we show in a model of phospholipid scrambling, a feature of apoptotic cells, that caveola stability is acutely affected by the scrambling. We conclude that the predominant plasmalemmal anionic lipid PtdSer is essential for proper Cav clustering, caveola formation, and caveola dynamics and that membrane scrambling can perturb caveolar stability.

show abstract

Molecular Characterization of Caveolin-induced Membrane Curvature

Cited by 96 publications

References 56 publications

Unraveling the architecture of caveolae

Unraveling the architecture of caveolae

Model for the architecture of caveolae based on a flexible, net-like assembly of Cavin1 and Caveolin discs

Phosphatidylserine dictates the assembly and dynamics of caveolae in the plasma membrane

Contact Info

Product

Resources

About