Kitano, R. | Search bioRxiv

bioRxiv2026

CAMSAP2 condensates drive a γ-TuRC-independent pathway for non-centrosomal microtubule nucleation

Microtubule nucleation is commonly viewed as a {gamma}-tubulin ring complex ({gamma}-TuRC)-templated process 1-3, yet many differentiated cells build extensive non-centrosomal microtubule arrays of unclear origin 4-6. Although spontaneous tubulin nucleation has long been observed in vitro as a {gamma}-TuRC-independent nucleation process 7-10, its mechanism and cellular relevance have remained unclear. Here we show that CAMSAP2, a microtubule minus-end-binding protein, links spontaneous nucleation to non-centrosomal microtubule organization. Cryo-electron microscopy (cryo-EM), high-speed atomic force microscopy (hsAFM), and molecular dynamics simulations reveal that CAMSAP2 lowers the nucleation barrier by straightening tubulin oligomers and promoting lateral protofilament interactions that drive sheet formation and closure into microtubules. hsAFM captures stepwise nucleation and early growth, revealing that tubulin rings can serve as productive intermediates rather than dead-end depolymerization products. CAMSAP2 further self-organizes through liquid-liquid phase separation (LLPS) to concentrate tubulin and assembly intermediates, thereby promoting efficient microtubule formation at non-centrosomal microtubule-organizing centers. In HeLa cells, dispersed CAMSAP2 condensates act as {gamma}-TuRC-independent microtubule-organizing centers alongside centrosomal asters, supporting a model in which spontaneous nucleation contributes to non-centrosomal microtubule biogenesis.

cell biology↗

bioRxiv2025

Lateralized vagal oxytocin signaling separately controls feeding and socioemotional functions via hypothalamic oxytocin signaling

Oxytocin neurons in the paraventricular hypothalamus (PVHOxt) regulate feeding, anxiety, and social behaviors. Activation of Oxt receptor (Oxtr) -expressing vagal sensory neurons engages these PVHOxt neurons and improves hyperphagic obesity; however, their roles in anxiety and sociability remain unclear. Here, we activated vagal Oxtr-expressing neurons in male mice using a single intraperitoneal (IP) Oxt injection or chemogenetics. IP Oxt reduced anxiety-like behavior, enhanced social interaction, and suppressed feeding while activating both vagal sensory neurons and PVHOxt neurons. These effects were abolished by chemogenetic inhibition of PVHOxt neurons or central Oxtr blockade. Subdiaphragmatic vagotomy revealed lateralized functions: right-side vagotomy eliminated anxiolytic and prosocial effects, whereas left-side vagotomy blocked feeding suppression. Consistently, chemogenetic activation of left-sided neurons suppressed feeding, while right-sided activation reduced anxiety and increased sociability. These findings identify Oxtr-expressing vagal sensory neurons as a major peripheral pathway in which left- and right-sided inputs differentially control feeding and socioemotional behaviors.

physiology↗

bioRxiv2025

A vagal sensory--hypothalamic oxytocin--brown adipose tissue pathway mediates cholecystokinin-induced thermogenesis

Thermoregulation is essential for survival in homeothermic animals. Vagal sensory nerves are well known to detect visceral signals and regulate physiological functions, including feeding, metabolism and immunity. However, their role in thermoregulation remains poorly understood. Cholecystokinin (CCK), a gut hormone released postprandially, activates vagal sensory nerves via CCK-A receptors (CCK-AR). Exogenous CCK has been reported to induce thermogenesis in the intrascapular brown adipose tissue (iBAT), but the involvement of vagal sensory nerves and the central neural mechanisms that mediate this effect are not fully understood. In this study, we assessed the thermogenic effect of intraperitoneally (I.P.) administered CCK-8 and investigated the underlying autonomic reflex pathways. I.P. CCK-8 transiently and dose-dependently increased rectal temperature. This response was significantly attenuated by pharmacological blockade of CCK-AR, subdiaphragmatic vagotomy, or knockdown of CCK-AR primarily targeting in vagal sensory neurons. In addition, CCK-8 activated sympathetic nerve activity via vagal afferents. CCK-8-induced thermogenesis was blunted by iBAT sympathectomy or {beta}3-adrenergic receptor blockade. Furthermore, I.P. CCK-8 activated oxytocin neurons in the paraventricular nucleus of the hypothalamus (PVHOXT). Chemogenetic inhibition of PVHOXT neurons or intracerebroventricular administration of an oxytocin receptor (OXTR) antagonist attenuated the thermogenic response. These findings demonstrate, for the first time, the full neural circuitry underlying CCK-induced thermogenesis by delineating its afferent input (CCK-AR-expressing vagal sensory neurons), central integrative hub (PVHOXT neurons and OXTR signaling), and efferent output (iBAT sympathetic nerves). This study further suggests that CCK-AR -expressing vagal sensory neurons may contribute to thermoregulation under physiological conditions in which CCK is endogenously released. Key points summaryO_LIVagal sensory nerves, which connect the gut and the brain, play a key role in regulating meal-related physiology, however their role in thermoregulation remains incompletely understood. C_LIO_LIThis study reveals for the first time the full autonomic reflex pathways underlying thermogenic effect of the gut hormone cholecystokinin (CCK), comprising afferent input (CCK-A receptor-expressing vagal afferents), a central integrative hub (oxytocin neurons in the hypothalamic paraventricular nucleus; PVHOXT neurons), and efferent output (intrascapular brown adipose tissue via sympathetic nerves). C_LIO_LIBoth CCK-A receptors-expressing vagal afferents and sympathetic nerves innervating brown adipose tissue are required for thermogenesis induced by exogenous CCK-8. C_LIO_LIActivation of PVHOXT neurons by CCK-8 is critically involved in mediating this thermogenic effect. C_LIO_LIThis newly identified gut-brain-fat axis may contribute to part of diet-induced thermogenesis, and its impairment could be involved in the development of metabolic disorders such as obesity. C_LI

physiology↗