Caveolae are plasma membrane invaginations that may play an important role in numerous cellular processes including transport, signaling, and tumor suppression. By targeted disruption of caveolin-1, the main protein component of caveolae, we generated mice that lacked caveolae. The absence of this organelle impaired nitric oxide and calcium signaling in the cardiovascular system, causing aberrations in endothelium-dependent relaxation, contractility, and maintenance of myogenic tone. In addition, the lungs of knockout animals displayed thickening of alveolar septa caused by uncontrolled endothelial cell proliferation and fibrosis, resulting in severe physical limitations in caveolin-1–disrupted mice. Thus, caveolin-1 and caveolae play a fundamental role in organizing multiple signaling pathways in the cell.

We demonstrate the existence of double-valued linear (infinite) spinorial representations of the group of general coordinate transformations. We discuss the topology of the group of general coordinate transformations and its subgroups GA(nR), GL(n,R), SL(nr) for n = 2,3,4, and the existence of a double covering. We present the construction of band-spinor representations of GL(n,R) in terms of Harish-Chandra modules. It is suggested that hadrons interact with gravitation as band-spinors of that type. In the metric-affine extension of general relativity, the hadron intrinsic hypermomentum is minimally coupled to the connection, in addition to the coupling of the energy momentum tensor to the vierbeins. The relativistic conservation of intrinsic hypermomentum fits the observed regularities of hadrons: SU(6) (∼ spin independence), scaling, and complex-J trajectories. The latter correspond to volume-preserving deformations (confinement?) exciting rotational bands.

Lateral assemblies of glycolipids and cholesterol, “rafts,” have been implicated to play a role in cellular processes like membrane sorting, signal transduction, and cell adhesion. We studied the structure of raft domains in the plasma membrane of non-polarized cells. Overexpressed plasma membrane markers were evenly distributed in the plasma membrane. We compared the patching behavior of pairs of raft markers (defined by insolubility in Triton X-100) with pairs of raft/non-raft markers. For this purpose we cross-linked glycosyl-phosphatidylinositol (GPI)-anchored proteins placental alkaline phosphatase (PLAP), Thy-1, influenza virus hemagglutinin (HA), and the raft lipid ganglioside GM1 using antibodies and/or cholera toxin. The patches of these raft markers overlapped extensively in BHK cells as well as in Jurkat T–lymphoma cells. Importantly, patches of GPI-anchored PLAP accumulated src-like protein tyrosine kinase fyn, which is thought to be anchored in the cytoplasmic leaflet of raft domains. In contrast patched raft components and patches of transferrin receptor as a non-raft marker were sharply separated. Taken together, our data strongly suggest that coalescence of cross-linked raft elements is mediated by their common lipid environments, whereas separation of raft and non-raft patches is caused by the immiscibility of different lipid phases. This view is supported by the finding that cholesterol depletion abrogated segregation. Our results are consistent with the view that raft domains in the plasma membrane of non-polarized cells are normally small and highly dispersed but that raft size can be modulated by oligomerization of raft components.

From Coils to Cages: Self-assembly strategies that mimic protein assembly, such as the formation of viral coats, often begin with simpler peptide assemblies. Fletcher et al. (p. 595 , published online 11 April; see the Perspective by Ardejani and Orner ) designed two coiled-coil peptide motifs, a heterodimer, and a homotrimer. Both peptides contained cysteine residues and could link through disulfide bonds, so that the trimer could form the vertices of a hexagonal network and the dimer its edges. However, these components are flexible and, rather than form extended sheets, they closed to form particles ∼100 nanometers in diameter.

Some insects, such as dragonflies, have evolved nanoprotrusions on their wings that rupture bacteria on contact. This has inspired the design of antibacterial implant surfaces with insect-wing mimetic nanopillars made of synthetic materials. Here, we characterise the physiological and morphological effects of mimetic titanium nanopillars on bacteria. The nanopillars induce deformation and penetration of the Gram-positive and Gram-negative bacterial cell envelope, but do not rupture or lyse bacteria. They can also inhibit bacterial cell division, and trigger production of reactive oxygen species and increased abundance of oxidative stress proteins. Our results indicate that nanopillars’ antibacterial activities may be mediated by oxidative stress, and do not necessarily require bacterial lysis.

The ESCRT-III complex is implicated in the reformation of the nuclear envelope; the CHMP2A component of ESCRT-III is directed to the forming nuclear envelope through classical ESCRT-assembly mechanisms, with the help of the p97 complex component UFD1, and provides an activity essential for nuclear envelope reformation. At an early stage of cell division in animal cells the nuclear envelope breaks down, and once cell division draws to a close at anaphase, the envelope must reform around the nuclei of the two daughter cells. It is known that the nuclear envelope is derived from the membranes of another organelle, the endoplasmic reticulum, and that it is sealed through a membrane fusion step, but the mechanism of fusion remains partially understood. Two groups report this week [in this issue of Nature] that this process is regulated by ESCRT-III, a protein complex best known for membrane constriction and sealing during various cellular processes. Harald Stenmark and colleagues show that ESCRT-III and two other proteins, VPS4 and spastin, cooperatively coordinate envelope fusion and spindle disassembly in a process mechanistically similar to the cytokinesis that ensures physical separation of the two daughter cells. Jeremy Carlton and colleagues find that the CHMP2A component of ESCRT-III is directed to the forming nuclear envelope where it localizes to sites of fusion through binding to CHMP4B, and with the help of UFD1 — a component of the p97 complex previously implicated in nuclear envelope fusion. During telophase, the nuclear envelope (NE) reforms around daughter nuclei to ensure proper segregation of nuclear and cytoplasmic contents1,2,3,4. NE reformation requires the coating of chromatin by membrane derived from the endoplasmic reticulum, and a subsequent annular fusion step to ensure that the formed envelope is sealed1,2,4,5. How annular fusion is accomplished is unknown, but it is thought to involve the p97 AAA-ATPase complex and bears a topological equivalence to the membrane fusion event that occurs during the abscission phase of cytokinesis1,6. Here we show that the endosomal sorting complex required for transport-III (ESCRT-III) machinery localizes to sites of annular fusion in the forming NE in human cells, and is necessary for proper post-mitotic nucleo-cytoplasmic compartmentalization. The ESCRT-III component charged multivesicular body protein 2A (CHMP2A) is directed to the forming NE through binding to CHMP4B, and provides an activity essential for NE reformation. Localization also requires the p97 complex member ubiquitin fusion and degradation 1 (UFD1). Our results describe a novel role for the ESCRT machinery in cell division and demonstrate a conservation of the machineries involved in topologically equivalent mitotic membrane remodelling events.