Membrane remodeling by BAR (Bin, Amphiphysin, RVS) domain-containing proteins, such as endophilins and amphiphysins, is integral to the process of endocytosis. However, little is known about the regulation of endocytic BAR domain activity. We have identified an interaction between the yeast Rvs167 N-BAR domain and calmodulin. Calmodulin-binding mutants of Rvs167 exhibited defects in endocytic vesicle release. In vitro, calmodulin enhanced membrane tubulation and constriction by wild-type Rvs167 but not calmodulin-binding-defective mutants. A subset of mammalian N-BAR domains bound calmodulin, and co-expression of calmodulin with endophilin A2 potentiated tubulation in vivo. These studies reveal a conserved role for calmodulin in regulating the intrinsic membrane-sculpting activity of endocytic N-BAR domains.

© 2014.A debilitating complication of breast cancer is the metastatic spread of tumor cells to the leptomeninges or cerebrospinal fluid (CSF). Patients diagnosed with this aggressive clinical syndrome, known as leptomeningeal carcinomatosis, have very poor

Ribosomes are molecular machines that function in polyribosome complexes to translate genetic information, guide the synthesis of polypeptides, and modulate the folding of nascent proteins. Here, we report a surprising function for polyribosomes as a result of a systematic examination of the assembly of a large ribonucleoprotein complex, the vault particle. Structural and functional evidence points to a model of vault assembly whereby the polyribosome acts like a 3D nanoprinter to direct the ordered translation and assembly of the multi-subunit vault homopolymer, a process which we refer to as polyribosome templating. Structure-based mutagenesis and cell-free in vitro expression studies further demonstrated the critical importance of the polyribosome in vault assembly. Polyribosome templating prevents chaos by ensuring efficiency and order in the production of large homopolymeric protein structures in the crowded cellular environment and might explain the origin of many polyribosome-associated molecular assemblies inside the cell.

Extrapulmonary manifestations of COVID-19 are associated with a much higher mortality rate than pulmonary manifestations. However, little is known about the pathogenesis of systemic complications of COVID-19. Here, we create a murine model of SARS-CoV-2-induced severe systemic toxicity and multiorgan involvement by expressing the human ACE2 transgene in multiple tissues via viral delivery, followed by systemic administration of SARS-CoV-2. The animals develop a profound phenotype within 7 days with severe weight loss, morbidity, and failure to thrive. We demonstrate that there is metabolic suppression of oxidative phosphorylation and the tricarboxylic acid (TCA) cycle in multiple organs with neutrophilia, lymphopenia, and splenic atrophy, mirroring human COVID-19 phenotypes. Animals had a significantly lower heart rate, and electron microscopy demonstrated myofibrillar disarray and myocardial edema, a common pathogenic cardiac phenotype in human COVID-19. We performed metabolomic profiling of peripheral blood and identified a panel of TCA cycle metabolites that served as biomarkers of depressed oxidative phosphorylation. Finally, we observed that SARS-CoV-2 induces epigenetic changes of DNA methylation, which affects expression of immune response genes and could, in part, contribute to COVID-19 pathogenesis. Our model suggests that SARS-CoV-2-induced metabolic reprogramming and epigenetic changes in internal organs could contribute to systemic toxicity and lethality in COVID-19.

Scar tissue size following myocardial infarction is an independent predictor of cardiovascular outcomes, yet little is known about factors regulating scar size. We demonstrate that collagen V, a minor constituent of heart scars, regulates the size of heart scars after ischemic injury. Depletion of collagen V led to a paradoxical increase in post-infarction scar size with worsening of heart function. A systems genetics approach across 100 in-bred strains of mice demonstrated that collagen V is a critical driver of postinjury heart function. We show that collagen V deficiency alters the mechanical properties of scar tissue, and altered reciprocal feedback between matrix and cells induces expression of mechanosensitive integrins that drive fibroblast activation and increase scar size. Cilengitide, an inhibitor of specific integrins, rescues the phenotype of increased post-injury scarring in collagen-V-deficient mice. These observations demonstrate that collagen V regulates scar size in an integrin-dependent manner.