Diabetes mellitus is a metabolic disorder approaching epidemic proportions. Non-alcoholic fatty liver disease (NAFLD) regularly coexists with metabolic disorders, including type 2 diabetes, obesity, and cardiovascular disease. Recently, we demonstrated that the voltage-dependent anion channel 1 (VDAC1) is involved in NAFLD. VDAC1 is an outer mitochondria membrane protein that serves as a mitochondrial gatekeeper, controlling metabolic and energy homeostasis, as well as crosstalk between the mitochondria and the rest of the cell. It is also involved in mitochondria-mediated apoptosis. Here, we demonstrate that the VDAC1-based peptide, R-Tf-D-LP4, affects several parameters of a NAFLD mouse model in which administration of streptozotocin (STZ) and high-fat diet 32 (STZ/HFD-32) led to both type 2 diabetes (T2D) and NAFLD phenotypes. We focused on diabetes, showing that R-Tf-D-LP4 peptide treatment of STZ/HFD-32 fed mice restored the elevated blood glucose back to close to normal levels, and increased the number and average size of islets and their insulin content as compared to untreated controls. Similar results were obtained when staining the islets for glucose transporter type 2. In addition, the R-Tf-D-LP4 peptide decreased the elevated glucose levels in a mouse displaying obese, diabetic, and metabolic symptoms due to a mutation in the obese (ob) gene. To explore the cause of the peptide-induced improvement in the endocrine pancreas phenotype, we analyzed the expression levels of the proliferation marker, Ki-67, and found it to be increased in the islets of STZ/HFD-32 fed mice treated with the R-Tf-D-LP4 peptide. Moreover, peptide treatment of STZ/HFD-32 fed mice caused an increase in the expression of β-cell maturation and differentiation PDX1 transcription factor that enhances the expression of the insulin-encoding gene, and is essential for islet development, function, proliferation, and maintenance of glucose homeostasis in the pancreas. This increase occurred mainly in the β-cells, suggesting that the source of their increased number after R-Tf-D-LP4 peptide treatment was most likely due to β-cell proliferation. These results suggest that the VDAC1-based R-Tf-D-LP4 peptide has potential as a treatment for diabetes.

The ESCRT machinery drive membrane remodeling in numerous processes in eukaryotes. Genes encoding for ESCRT proteins have been identified in Asgard archaea, a newly discovered superphylum, currently recognized as the ancestor of all eukaryotes. This begs the question of the functional evolutionary origin of this machinery and its conservation across lineages. Here, we find that Asgard-ESCRT’s exhibit conserved DNA-binding properties, which is derived from recruitment of specific members. We show that Asgard-ESCRT-III/VPS4 homologs interact with one another inside mammalian cells, associate with chromatin, and recruit their counterparts to organize in discrete foci in the mammalian nucleus. This is congruent with human-ESCRT-III homologs. We find that human- and Asgard-ESCRT-IIIs associate with chromatin via the same N terminal domain, and that human-ESCRT-III can recruit Asgard-VPS4 to the nucleus to form foci. Therefore, ESCRTs possess chromatin binding properties that were preserved through the billion years of evolution that separate Asgard and human cells.

The archaeal Asgard superphylum currently stands as the most promising prokaryotic candidate, from which eukaryotic cells emerged. This unique superphylum encodes for eukaryotic signature proteins (ESP) that could shed light on the origin of eukaryotes, but the properties and function of these proteins is largely unresolved. Here, we set to understand the function of an Asgard archaeal protein family, namely the ESCRT machinery, that is conserved across all domains of life and executes basic cellular eukaryotic functions, including membrane constriction during cell division. We find that ESCRT proteins encoded in Loki archaea, express in mammalian and yeast cells, and that the Loki ESCRT-III protein, CHMP4-7, resides in the eukaryotic nucleus in both organisms. Moreover, Loki ESCRT-III proteins associated with chromatin, recruited their AAA-ATPase VPS4 counterpart to organize in discrete foci in the mammalian nucleus, and directly bind DNA. The human ESCRT-III protein, CHMP1B, exhibited similar nuclear properties and recruited both human and Asgard VPS4s to nuclear foci, indicating interspecies interactions. Mutation analysis revealed a role for the N terminal region of ESCRT-III in mediating these phenotypes in both human and Asgard ESCRTs. These findings suggest that ESCRT proteins hold chromatin binding properties that were highly preserved through the billion years of evolution separating Asgard archaea and humans. The conserved chromatin binding properties of the ESCRT membrane remodeling machinery, reported here, may have important implications for the origin of eukaryogenesis.

The ESCRT machinery mediate membrane remodeling in numerous processes in cells including cell division and nuclear membrane reformation. The identification of ESCRT homologs in Asgard archaea, currently considered the closest ancestor of eukaryotes, suggests a role for ESCRTs in the membrane remodeling processes that occurred during eukaryogenesis. Yet, the function of these distant ESCRT homologs is mostly unresolved. Here we show that Asgard ESCRT-III proteins self-assemble into homo- and hetero- helical tubes, a hallmark of the eukaryotic ESCRT system. Asgard ESCRT-III tube assembly was facilitated in the presence of DNA and inhibited by DNAase. Notably, Asgard ESCRT-III filaments remodeled eukaryotic-like membrane vesicles, also in the presence of DNA, indicating an ancient role for the ESCRT complex in membrane remodeling, that may involve DNA binding. The ability of Asgard archaeal ESCRTs to remodel eukaryotic-like membranes, places them at the junction between prokaryotes and eukaryotes, substantiating a role for ESCRTs in eukaryogenesis