The following chemicals and reagents were used: Dounce homogenizer (DWK Life Sciences, 885302-0002); Pierce anti-HA magnetic beads (Thermo Scientific, 88837); Pierce anti-Flag magnetic agarose (Thermo Scientific, A36797); anti-Flag M2 magnetic beads (Sigma Millipore, M8823); Pierce protein A/G magnetic beads (Thermo...

In a groundbreaking study published in Nature, researchers have unveiled a comprehensive structural and functional map of human early endosome complexes, shedding new light on the dynamic interplay of ion transporters and their accessory proteins within this critical cellular compartment. This study notably identifies TMEM9 and TMEM9B as essential core subunits of the endosomal chloride/proton antiporters CLCN3, CLCN4, and CLCN5, reshaping our understanding of endosomal ion homeostasis and its implications in neuronal health and disease.

Interferon-induced transmembrane (IFITM) proteins are potent innate immune factors that restrict an array of viruses at the entry stage of infection. We previously characterized a GxxxG motif in the CD225 domain of human IFITM3 that mediates its multimerization, which is essential for the reduction of membrane fluidity by IFITM3 and for its antiviral activity against Influenza A virus. Here, using an unbiased approach coupling immunoprecipitation with mass spectrometry, we show that the GxxxG motif is also important for the interaction of IFITM3 with other proteins, including IFITM1. While IFITM1 is primarily regarded as a cell surface protein that restricts the entry of viruses fusing at the plasma membrane, this model is based mostly on overexpression studies and is at odds with some studies showing that it can restrict endocytic viruses. Here, we show that endogenous IFITM1 and IFITM3 co-reside in membranes of acidic late endosomes and lysosomes (endolysosomes) and form a protein-protein complex as determined by co-immunoprecipitation and proximity ligation assay. Knockdown of endogenous IFITM3 resulted in enhanced localization of IFITM1 at the plasma membrane, indicating that IFITM3 promotes IFITM1 localization to endolysosomes. To assess the antiviral protection conferred by endogenous IFITM1 and IFITM3 against viruses fusing at endolysosomal membranes, we measured cell entry mediated by the Influenza A fusogen hemagglutinin (HA). While knockdown of IFITM3 significantly boosted HA-mediated entry, combined knockdown of both IFITM3 and IFITM1 boosted entry even further. These results suggest that endogenous IFITM1 restricts Influenza A virus entry in a manner that is non-redundant with IFITM3, and that IFITM1 and IFITM3 inhibit virus entry in a cooperative manner.

Lysosome damage activates multiple pathways to prevent lysosome-dependent cell death, including a repair mechanism involving endoplasmic reticulum (ER…

Optical imaging is central to biomedical research. We will host a weeklong microscopy bootcamp training at the Marine Biological Laboratory. This bootcamp is planned to train graduate students and pos...

PEPFAR’s computer systems also are being taken offline, a sign that the program may not return, as Republican critics had hoped.

US experts said the sudden pause came as a surprise and would set back efforts to contain health threats abroad.

H5N1 is adapting to new mammal hosts, raising the possibility of the virus spreading between humans.

Lysosomes are best known for their roles in inflammatory responses via autophagy. Here, Xing et al., find that lysosomes regulate macrophage inflammatory responses by finely controlling interleukin-1β...

Cytochrome bd from Mycobacterium tuberculosis (Mtbd) is a menaquinol oxidase that has gained interest as an antibiotic target because of its importance in survival under infectious conditions. Mtbd co...

Programmed ribosomal frameshifting is a process where a proportion of ribosomes change their reading frame on an mRNA, rephasing the ribosome relative to the mRNA. While frameshifting is commonly employed by viruses, very few phylogenetically conserved examples are known in nuclear encoded genes and some of the evidence is controversial. Here we report a +1 frameshifting event during decoding of the human gene PLEKHM2. This frameshifting occurs at the sequence UCC\_UUU\_CGG, which is conserved in vertebrates and is similar to an influenza virus sequence that frameshifts with similar efficiency. The new C-terminal domain generated by this frameshift forms an α-helix, which relieves PLEKHM2 from autoinhibition and allows it to move to the tips of cells via association with kinesin-1 without requiring activation by ARL8. Reintroducing both the canonically-translated and frameshifted protein are necessary to restore normal contractile function of PLEKHM2-knockout cardiomyocytes, demonstrating the necessity of frameshifting for normal cardiac activity. ### Competing Interest Statement The authors have declared no competing interest.

Published in Science advances