Morselli, E. | bioRxiv Science

bioRxiv2026

Galectin-8 regulates primary cilium in hypothalamic neurons through anL-type calcium channel/Aurora kinaseA/HDAC6 pathway impacting body energy balance

OBJETIVEFood intake, energy expenditure, and metabolic homeostasis depend on hypothalamic neurons responses to peripheral signals, such as leptin, involving the primary cilium (PC). The PC is crucial for signal transduction and is dynamically regulated by assembly/disassembly or reabsorption of its microtubules-based axoneme. Absence or reduction in the length of PC is associated with obesity and type-2 diabetes (T2D). In other cellular systems, PC reabsorption is primarily regulated by calcium-mediated activation of the Aurora kinase A (AurkA)/histone deacetylase C6 (HDAC6) axis, which promotes axonemal disassembly. Here, we explore the role of Galectin-8 (Gal-8), a glycan-binding protein, in regulating PC structure and signaling related to metabolic parameters in hypothalamic neurons. METHODSGal-8 effects were assessed in hypothalamic Clu-177 cells by analyzing the PC presence and length by immunofluorescence, PC dynamics, and intracellular calcium changes by in vivo cell imaging, activation of FAK, Src, AurkA, HDAC6 and STAT3 by immunoblot, and Gal-8 interactions with {beta}1-integrins by pull-down assays. Gal-8-KO mice were used to evaluate PC length in hypothalamic neurons, metabolic phenotype, and responses to Gal-8 intranasal administration. RESULTSIn Clu-177 cells, Gal-8 induced PC reabsorption and reduced responsiveness to leptin signaling towards STAT3 activation. PC reabsorption involves glycan-mediated Gal-8 interactions with a5b1 and a3b1 integrins, activation of FAK and Src leading to calcium influx through L-type calcium channels (LTCC), and subsequent AurkA/HDAC6 axis activation. Gal-8-KO mice showed longer PC in hypothalamic neurons, higher STAT3 activation, decreased body weight and food intake, improved glucose tolerance, higher locomotor activity, and a glycolytic respiratory exchange rate (RER). Daily intranasal Gal-8 administration for 4 days restored hypothalamic PC length and STAT3 signaling, as well as RER in Gal-8-KO mice to the level of WT mice. CONCLUSIONSEndogenous Gal-8 is required to maintain PC structure and leptin signaling in hypothalamic neurons, impacting body weight, energy balance, and glucose homeostasis. The mechanism involves calcium influx via LTCC downstream of b1-integrin/FAK/Src signaling and subsequent AurkA/HDAC6 axis activation. Both Gal-8 and the AurkA/HDAC6 axis may offer new therapeutic opportunities for treating metabolic diseases characterized by ciliogenesis impairment, including obesity and type-2 diabetes.

cell biology↗

bioRxiv2023

Acute resistance exercise induces mitophagy and mitophagomes on subsarcolemmal clefts in human skeletal muscle: Focus on BNIP3L/NIX40 as a mitophagy flux marker

ObjectiveMitochondrial dynamics and quality control in skeletal muscle are central to healthy metabolism. Resistance exercise is a recognized tool for improving skeletal muscle function; however, its effect on mitochondria is still not fully understood. We investigated the impact of resistance exercise on mitochondrial morphology and mitophagy in human skeletal muscle. MethodsEight healthy men performed resistance exercise on one leg, and muscle biopsies were subsequently obtained from the resting leg (Rest) and the exercised leg (Ex) to measure protein abundance and mitochondrial morphology. Additionally, muscle biopsies were obtained from twelve healthy men, and the abundance of BNIP3L protein was correlated with muscle cell and whole body health markers. ResultsEx increased p-Drp1 and decreased MFN2, Parkin, and BNIP3L protein levels. Electron microscopy indicated an increase in mitochondrial circularity, cristae abnormality, and mitophagosome structures in Ex, with a marked increase in subsarcolemmal mitophagosomes. We also identified mitophagosomes outside the muscle. Experiments in human myotubes showed a severe decrease in BNIP3L protein in response to CCCP-induced mitochondrial damage with and without bafilomycin. A positive correlation was found between BNIP3L and exercise RQ, HOMA index, while a negative correlation was found with mitophagosomes abundance and VO2max. ConclusionOur study describes the effect of resistance exercise on mitochondrial dynamics and mitophagy in skeletal muscle, demonstrating induction of mitochondrial fission and mitophagy in the exercised leg. Moreover, we propose BNIP3L as a potential regulator and marker of mitophagy flux.

physiology↗