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Membranes are protein and lipid structures that surround cells and other biological compartments. We present a conceptual model wherein all membranes are organized into structural and functional zones. The assembly of zones such as receptor clusters, protein-coated pits, lamellipodia, cell junctions, and membrane fusion sites is explained to occur through a protein-lipid code. This challenges the theory that lipids sort proteins after forming stable membrane subregions independently of proteins.

Alzheimer’s disease (AD) is the most common cause of dementia worldwide. Despite extensive research and targeting of the main molecular components of the disease, beta-amyloid (Aβ) and tau, there are currently no treatments that alter the progression of the disease. Here, we examine the effects of two specific kinase inhibitors for calcium/calmodulin-dependent protein kinase type 1D (CaMK1D) on Aβ-mediated toxicity, using mouse primary cortical neurons. Tau hyperphosphorylation and cell death were used as AD indicators. These specific inhibitors were found to prevent Aβ induced tau hyperphosphorylation in culture, but were not able to protect cells from Aβ induced toxicity. While inhibitors were able to alter AD pathology in cell culture, they were insufficient to prevent cell death. With further research and development, these inhibitors could contribute to a multi-drug strategy to combat AD.

Key Points The Gram-negative outer membrane protein (OMP) family includes proteins that are associated with basic physiological functions, virulence and multidrug resistance, and therefore plays a fundamental part in the maintenance of cellular viability. Understanding how these proteins are targeted and folded into this membrane is crucial, as it could offer important medical benefits. Compounds that inhibit key stages of this process would block key stages of OMP biogenesis, thereby inhibiting essential physiological, pathogenic and drug resistance functions, and could prove useful in combating diverse pathogens, including Pseudomonas aeruginosa , Neisseria meningitidis and Salmonella enterica . OMP biogenesis in Gram-negative bacteria has, until recently, remained a largely unknown mechanism. However, over the past 3 years, a complex of proteins has been discovered that is known as the β-barrel assembly machinery (BAM) and is responsible for folding and inserting OMPs into the membrane. Recent advances in our understanding of the molecular basis of OMP biogenesis in Gram-negative bacteria are discussed. Emphasis is placed on analysis of the recently discovered component structures and accessory interactions, in particular with the periplasmic chaperones DegP, Skp and SurA, which are known to interact with OMPs. The mechanisms that the BAM complex might use in the folding and insertion of OMPs into the membrane are also discussed. Considerable advances have been made in the field of outer membrane protein biogenesis during the past year. The β-barrel assembly machinery (BAM) mediates efficient insertion of folded β-barrels into the outer membrane of Gram-negative bacteria. The role of the BAM in the folding of membrane proteins is discussed in this Review. The folding of transmembrane proteins into the outer membrane presents formidable challenges to Gram-negative bacteria. These proteins must migrate from the cytoplasm, through the inner membrane and into the periplasm, before being recognized by the β-barrel assembly machinery, which mediates efficient insertion of folded β-barrels into the outer membrane. Recent discoveries of component structures and accessory interactions of this complex are yielding insights into how cells fold membrane proteins. Here, we discuss how these structures illuminate the mechanisms responsible for the biogenesis of outer membrane proteins.

Sorting nexins anchor trafficking machines to membranes by binding phospholipids. The paradigm of the superfamily is sorting nexin 3 (SNX3), which localizes to early endosomes by recognizing phosphatidylinositol 3-phosphate (PI3P) to initiate retromer-mediated segregation of cargoes to the trans-Golgi network (TGN). Here we report the solution structure of full length human SNX3, and show that PI3P recognition is accompanied by bilayer insertion of a proximal loop in its extended Phox homology (PX) domain. Phosphoinositide (PIP) binding is completely blocked by cancer-linked phosphorylation of a conserved serine beside the stereospecific PI3P pocket. This “PIP-stop” releases endosomal SNX3 to the cytosol, and reveals how protein kinases control membrane assemblies. It constitutes a widespread regulatory element found across the PX superfamily and throughout evolution including of fungi and plants. This illuminates the mechanism of a biological switch whereby structured PIP sites are phosphorylated to liberate protein machines from organelle surfaces. Sorting nexin 3 (SNX3) is a phosphatidylinositol 3-phosphate binding protein that localizes to early endosomes. Here the authors use NMR to resolve SNX3′s membrane interactions, revealing that membrane binding is regulated through phosphorylation of a conserved serine by its lipid recognition site.

In the past few years there has been a growth in the use of nanoparticles for stabilizing lipid membranes that contain embedded proteins. These bionanoparticles provide a solution to the challenging problem of membrane protein isolation by maintaining a lipid bilayer essential to protein integrity and activity. We have previously described the use of an amphipathic polymer （poly（styrene-co-maleic add）, SMA） to produce discoidal nanoparticles with a lipid bilayer core containing the embedded protein. However the structure of the nanoparticle itself has not yet been determined. This leaves a major gap in understanding how the SMA stabilizes the encapsulated bilayer and how the bilayer relates physically and structurally to an unencapsulated lipid bilayer. In this paper we address this issue by describing the structure of the SMA lipid particle （SMALP） using data from small angle neutron scattering （SANS）, electron microscopy （EM）, attenuated total reflection Fourier transform infrared spectroscopy （ATR-FTIR）, differential scanning calorimetry （DSC） and nuclear magnetic resonance spectroscopy （NMR）. We show that the particle is disc shaped containing a polymer ＂bracelet＂ encircling the lipid bilayer. The structure and orientation of the individual components within the bilayer and polymer are determined showing that styrene moieties within SMA intercalate between the lipid acyl chains. The dimensions of the encapsulated bilayer are also determined and match those measured for a natural membrane. Taken together, the description of the structure of the SMALP forms the foundation for future development and applications of SMALPs in membrane protein production and analysis.

Early stages of colorectal cancer (CRC) development are characterized by a complex rewiring of transcriptional networks resulting in changes in the expression of multiple genes. Here, we demonstrate that the deletion of a poorly studied tetraspanin protein Tspan6 in Apcmin/+ mice, a well-established model for premalignant CRC, resulted in increased incidence of adenoma formation and tumor size. We demonstrate that the effect of Tspan6 deletion results in the activation of EGF-dependent signaling pathways through increased production of the transmembrane form of TGF-α (tmTGF-α) associated with extracellular vesicles. This pathway is modulated by an adaptor protein syntenin-1, which physically links Tspan6 and tmTGF-α. In support of this, the expression of Tspan6 is frequently decreased or lost in CRC, and this correlates with poor survival. Furthermore, the analysis of samples from the epidermal growth factor receptor (EGFR)–targeting clinical trial (COIN trial) has shown that the expression of Tspan6 in CRC correlated with better patient responses to EGFR-targeted therapy involving Cetuximab. Importantly, Tspan6-positive patients with tumors in the proximal colon (right-sided) and those with KRAS mutations had a better response to Cetuximab than the patients that expressed low Tspan6 levels. These results identify Tspan6 as a regulator of CRC development and a potential predictive marker for EGFR-targeted therapies in CRC beyond RAS pathway mutations.

Hsp90 is a dimeric molecular chaperone essential for the maturation, activation, stabilization, and folding of numerous clients required for cellular functions. Hsp90 progresses through a dynamic ATP-driven conformational cycle that is precisely regulated by accessory proteins known as co-chaperones. Here, we show that the isolated N-domain of Aha1 (Aha1N156) binds the apo state of Hsp90 but fails to associate with the closed, nucleotide-bound state. In contrast, the full-length Aha1 binds Hsp90 in both conformational states, suggesting a key role for the Aha1 C domain in binding to the nucleotide-bound, closed state of Hsp90. Surprisingly, the Aha1 paralogue Hch1, which corresponds to the Aha1 N domain, was capable of binding to Hsp90 in both the apo and nucleotide-bound states. Interestingly, the addition of a 14 amino acid residues section of the linker to the Aha1 N domain restores closed-state binding, indicating an unexpected role for the linker in stabilizing nucleotide-dependent interactions. Analysis of yeast-human Aha1 chimeras further demonstrates that the C-terminal domain of Aha-type co-chaperones serves as an evolutionarily conserved anchoring module, enabling stable engagement of the ATP-bound state despite significant sequence divergence. This work allows us to propose a model in which the Aha1 C domain allows for the repositioning of the Aha1 N domain that occurs during the transition from the apo to the ATP-bound state of Hsp90.

Human papillomaviruses enter host cells via a clathrin-independent endocytic pathway involving tetraspanin proteins. However, post-endocytic trafficking required for virus capsid disassembly remains unclear. Here we demonstrate that the early trafficking pathway of internalised HPV particles involves tetraspanin CD63, syntenin-1 and ESCRT-associated adaptor protein ALIX. Following internalisation, viral particles are found in CD63-positive endosomes recruiting syntenin-1, a CD63-interacting adaptor protein. Electron microscopy and immunofluorescence experiments indicate that the CD63-syntenin-1 complex controls delivery of internalised viral particles to multivesicular endosomes. Accordingly, infectivity of high-risk HPV types 16, 18 and 31 as well as disassembly and post-uncoating processing of viral particles was markedly suppressed in CD63 or syntenin-1 depleted cells. Our analyses also present the syntenin-1 interacting protein ALIX as critical for HPV infection and CD63-syntenin-1-ALIX complex formation as a prerequisite for intracellular transport enabling viral capsid disassembly. Thus, our results identify the CD63-syntenin-1-ALIX complex as a key regulatory component in post-endocytic HPV trafficking.

The omics disciplines remain largely distinct sciences due to the necessity of separating molecular classes for different assays. For example, water-soluble and lipid bilayer-bound proteins and metabolites are usually studied separately. Nonetheless, it is at the interface between these sciences where biology happens. That is, lipid-interacting proteins typically recognize and transduce signals and regulate the flow of metabolites in the cell. Technologies are emerging to converge the omics. It is now possible to separate intact membrane:protein assemblies (memteins) directly from intact cells or cell membranes. Such complexes mediate complete metabolon, receptor, channel, and transporter functions. The use of poly(styrene-co-maleic acid) (SMA) copolymers has allowed their separation in a single step without any exposure to synthetic detergents or artificial lipids. This is a critical development as these agents typically strip away biological lipids, signals, and metabolites from their physiologically-relevant positions on proteins. The resulting SMA lipid particles (SMALPs) represent native nanodiscs that are suitable for elucidation of structures and interactions that occur in vivo. Compatible tools for resolving the contained memteins include X-ray diffraction (XRD), cryo-electron microscopy (cryoEM), mass spectrometry (MS), and nuclear magnetic resonance (NMR) spectroscopy. Recent progress shows that memteins are more representative than naked membrane proteins devoid of natural lipid and is driving the development of next generation polymers.

Phosphatases are increasingly recognized as critical regulators of cancer biology, with important roles in both tumor cells and the tumor immune microenvironment (TIME). These enzymes modulate intracellular signaling pathways that control tumor growth, immune evasion, and metastasis. Although phosphatases were once considered undruggable, recent advances have highlighted their therapeutic potential. Despite growing evidence, phosphatases remain underexplored as drug targets, with no approved therapies to date. This review presents an in‐depth overview of phosphatase classification based on catalytic domain similarities and explores their diverse functions as tumor suppressors, oncogenic drivers, or context‐dependent regulators. We describe how phosphatases such as PTPN6, PTPN22, and DUSPs regulate key pathways like RAS/MAPK and PI3K/AKT in both tumor and immune cells. Additionally, we discuss the role of phosphatases in shaping the tumor microenvironment through exosome secretion. This review highlights current therapeutic strategies, including small molecules and antibodies, and their synergistic effects with kinase inhibitors and immune checkpoint blockade. By summarizing recent advances, this paper underscores the need for deeper mechanistic insights into phosphatase function in cancer and immunity. Understanding these mechanisms will be key to unlocking their potential as novel therapeutic targets in oncology. Schematic depiction of the role of phosphatases in cancer, highlighting their involvement in proliferation, exosome secretion, and immunosuppression. The SHP2 crystal structure (PDB:5EHR) is shown as the representative phosphatase.