bims-lypmec 2025-03-09 papers

Anal Chem. 2025 Mar 06.

Near-Infrared Fluorescent Lysosomal Viscosity Probe with Strong Solid Fluorescence for Rapid Imaging of Rheumatoid Arthritis.

Siyu Jiang, Zhoupeng Zheng, Yijia Liu, Xiaodong Tan, Guoqiang Feng.

Rheumatoid arthritis (RA) is a chronic disease of widespread concern worldwide, and there is an urgent need to develop sensitive methods for the rapid detection of RA. Previous studies have shown that RA is closely related to lysosomal dysfunction. Lysosomal viscosity is an important microenvironmental parameter reflecting the state of lysosomes, but due to the lack of probes to demonstrate the correlation between lysosomal viscosity and RA, the changes in lysosomal viscosity during RA remain unclear. For this purpose, we report herein a lysosome-targeted near-infrared fluorescent molecular rotor probe DSMP to investigate the correlation between lysosomal viscosity and RA. This probe utilizes dicyanomethylene-4H-benzothiopyran as an electron acceptor in the fluorophore and a piperazine unit as an electron donor and targeting group for lysosomes. In addition, DSMP shows strong solid fluorescence and a sensitive response to viscosity and can effectively target lysosomes to detect changes in lysosomal viscosity in live cells. Based on this, we established a mouse model of RA using λ-carrageenan. Mice imaging studies show that DSMP can quickly image RA, and RA tissues exhibit fluorescence signals significantly brighter than those of normal joint tissues. This indicates an increase in lysosomal viscosity during RA; therefore, lysosomal viscosity can serve as an indicator for rapid detection of RA, and DSMP can be an effective tool for RA imaging and research.

DOI: https://doi.org/10.1021/acs.analchem.4c06455

J Biol Chem. 2025 Mar 04. pii: S0021-9258(25)00230-3. [Epub ahead of print] 108381

The ROGDI protein mutated in Kohlschutter-Tonz syndrome is a novel subunit of the Rabconnectin-3 complex implicated in V-ATPase assembly.

Samuel R Winkley, Patricia M Kane.

V-ATPases are highly conserved ATP-driven rotary proton pumps found widely among eukaryotes that are composed of two subcomplexes: V1 and V0. V-ATPase activity is regulated in part through reversible disassembly, during which V1 physically separates from V0 and both subcomplexes become inactive. Reassociation of V1 to V0 reactivates the complex for ATP-driven proton pumping and organelle acidification. V-ATPase reassembly in S. cerevisiae requires the RAVE complex (Rav1, Rav2, and Skp1) and higher eukaryotes, including humans, utilize the Rabconnectin-3 complex. Mammalian Rabconnectin-3 has two subunits: Rabconnectin-3α and Rabconnectin-3β. Rabconnectin-3α isoforms are homologous to Rav1, but there is no known Rav2 homolog and the molecular basis of the interaction between the Rabconnectin-3α and β subunits is unknown. We identified ROGDI as a Rav2 homolog and novel Rabconnectin-3 subunit. ROGDI mutations cause Kohlschutter-Tonz syndrome, an epileptic encephalopathy with amelogenesis imperfecta that has parallels to V-ATPase-related disease. ROGDI shares extensive structural homology with yeast Rav2 and can functionally replace Rav2 in yeast. ROGDI binds to the N-terminal domains of both Rabconnectin-3 α and β, similar to Rav2 binding to Rav1. Molecular modeling suggests that ROGDI may bridge the two Rabconnectin-3 subunits. ROGDI co-immunoprecipitates with Rabconnectin-3 subunits from detergent-solubilized lysates and is present with them in immunopurified lysosomes of mammalian cells. In immunofluorescence microscopy, ROGDI partially localizes with Rabconnectin-3α in acidic, perinuclear lysosomes. The discovery of ROGDI as a novel Rabconnectin-3 interactor sheds new light on both Kohlschutter-Tonz syndrome and the mechanisms behind mammalian V-ATPase regulation.

Keywords: ATPase; DMXL1; ROGDI; Rabconnectin-3; V-ATPase; WDR7; lysosomal acidification; lysosome; protein assembly; protein-protein interaction

DOI: https://doi.org/10.1016/j.jbc.2025.108381

J Cell Biol. 2025 Apr 07. pii: e202410013. [Epub ahead of print]224(4):

Any1 is a phospholipid scramblase involved in endosome biogenesis.

Jieqiong Gao, Rico Franzkoch, Cristian Rocha-Roa, Olympia Ekaterini Psathaki, Michael Hensel, Stefano Vanni, Christian Ungermann.

Endosomes are central organelles in the recycling and degradation of receptors and membrane proteins. Once endocytosed, such proteins are sorted at endosomes into intraluminal vesicles (ILVs). The resulting multivesicular bodies (MVBs) then fuse with the lysosomes, leading to the degradation of ILVs and recycling of the resulting monomers. However, the biogenesis of MVBs requires a constant lipid supply for efficient ILV formation. An ER-endosome membrane contact site has been suggested to play a critical role in MVB biogenesis. Here, we identify Any1 as a novel phospholipid scramblase, which functions with the lipid transfer protein Vps13 in MVB biogenesis. We uncover that Any1 cycles between the early endosomes and the Golgi and colocalizes with Vps13, possibly at a here-discovered potential contact site between lipid droplets (LDs) and endosomes. Strikingly, both Any1 and Vps13 are required for MVB formation, presumably to couple lipid flux with membrane homeostasis during ILV formation and endosome maturation.

DOI: https://doi.org/10.1083/jcb.202410013

J Mol Cell Cardiol. 2025 Feb 26. pii: S0022-2828(25)00037-9. [Epub ahead of print]

Lipotoxicity as a therapeutic target in the type 2 diabetic heart.

Trang Luong, Seonbu Yang, Jaetaek Kim.

Cardiac lipotoxicity, characterized by excessive lipid accumulation in the cardiac tissue, is a critical contributor to the pathogenesis of diabetic heart. Recent research has highlighted the key mechanisms underlying lipotoxicity, including mitochondrial dysfunction, endoplasmic reticulum stress, inflammation, and cell apoptosis, which ultimately impair the cardiac function. Various therapeutic interventions have been developed to target these pathways, mitigate lipotoxicity, and improve cardiovascular outcomes in diabetic patients. Given the global escalation in the prevalence of diabetes and the urgent demand for effective therapeutic approaches, this review focuses on how targeting cardiac lipotoxicity may be a promising avenue for treating diabetes.

Keywords: Cardiac lipotoxicity; Diabetic heart; Lipid accumulation; Lipid metabolism

DOI: https://doi.org/10.1016/j.yjmcc.2025.02.010

J Cell Biol. 2025 May 05. pii: e202407021. [Epub ahead of print]224(5):

Vacuoles provide the source membrane for TORC1-containing signaling endosomes.

Kenji Muneshige, Riko Hatakeyama.

Organelle biogenesis is fundamental to eukaryotic cell biology. Yeast signaling endosomes were recently identified as a signaling platform for the evolutionarily conserved Target of Rapamycin Complex 1 (TORC1) kinase complex. Despite the importance of signaling endosomes for TORC1-mediated control of cellular metabolism, how this organelle is generated has been a mystery. Here, we developed a system to induce synchronized de novo formation of signaling endosomes, enabling real-time monitoring of their biogenesis. Using this system, we identify vacuoles as a membrane source for newly formed signaling endosomes. Membrane supply from vacuoles is mediated by the CROP membrane-cutting complex, consisting of Atg18 PROPPIN and retromer subunits. The formation of signaling endosomes requires TORC1 activity, suggestive of a tightly regulated process. This study unveiled the first mechanistic principles and molecular participants of signaling endosome biogenesis.

DOI: https://doi.org/10.1083/jcb.202407021

Sci Rep. 2025 Mar 03. 15(1): 7384

Remodeling of the cardiac striatin interactome and its dynamics in the diabetic heart.

Stephanie Chacar, Wael Abdrabou, Cynthia Al Hageh, Liaqat Ali, Thenmozhi Venkatachalam, Pierre Zalloua, M-Saadeh Suleiman, Frank Christopher Howarth, Ali A Khraibi, Moni Nader.

Diabetic cardiomyopathy (DbCM) is a silent and complex condition involving numerous signaling pathways that impair cardiomyocyte metabolism and cardiac performance. Striatin (STRN) is a multifaceted protein that binds metabolic proteins, yet its role in diabetic heart remains unexplored. Here we characterized the cardiac STRN interactome by performing immunoprecipitation on left ventricle (LV) proteins from control and diabetic hearts (rats treated with streptozotocin for 24 weeks) to dissect its derivative protein complex. Diabetic rats exhibited pathological heart remodeling characterized by increased heart weight/body weight ratio, elevated levels of Atrial Natriuretic Factor (ANF), and altered expression of alpha and beta-myosin heavy chain isoforms. Notably, STRN expression mirrored that of the remodeling marker ANF across all cardiac chambers. Proteomic analysis yielded 247 proteins interacting with STRN exclusively in diabetic LV, 94 in both control and diabetic LV, and 11 only in control LV. STRN retained a higher interaction with some STRN interacting phosphatase and kinase complex (STRIPAK) proteins (i.e. protein phosphatase 2A (PP2A), and sarcolemmal associated membrane protein (SLMAP)) in diabetic LV, indicating a preserved role of this signalosome in diabetic settings. Functional enrichment and gene ontology revealed that the STRN interactome in diabetic LV carried signalosomes related to cardiac contractility, endoplasmic reticulum stress, mitochondrial function, and apoptotic processes. Western blot experiments confirmed the interaction between STRN and SLMAP in both control and diabetic heart. These data suggest a pivotal role for the STRN signalosome in cardiometabolic disorders, potentially paving the way for novel therapeutic management of DbCM. Targeting the STRN interactome in DbCM, mainly the first-line interactors SLMAP, PP2A, and Cav-1 may offer hope for patients with diabetes-induced cardiac injuries.

Keywords: Diabetes; Diabetic cardiomyopathy; Metabolic Disease; Signalosomes; Striatin interactome

DOI: https://doi.org/10.1038/s41598-025-91098-6