Dynamic regulation of hypothalamic NPY2R-positive primary cilia by nutritional states.

Primary cilia are specialized signaling organelles that concentrate selected G protein-coupled receptors and are important in neuronal and metabolic regulation. Neuropeptide Y receptor 2 (NPY2R), a receptor implicated in feeding and energy homeostasis, localizes to neuronal primary cilia in the hypothalamus. Although fasting-associated shortening of NPY2R-positive cilia in the arcuate nucleus (ARC) has recently been reported, it remains unclear whether this response reflects direct, ligand-driven structural remodeling of NPY2R-positive cilia, whether distinct nutritional states differentially regulate this receptor-defined ciliary compartment across feeding-related brain regions, and which intracellular mechanisms mediate these changes. Here, we show that neuropeptide Y (NPY) directly induces structural retraction of NPY2R-positive primary cilia, that nutritional states differentially remodel this receptor-defined ciliary compartment in a region-specific manner, and that NPY-driven ciliary retraction is mediated by Gi/o-dependent Akt/JNK signaling. In vivo, fasting shortened NPY2R-positive primary cilia in two of five examined regions, the ARC and ventromedial hypothalamus, whereas the adenylyl cyclase 3 (AC3)-positive ciliary population remained unchanged. Conversely, chronic high-fat diet feeding induced a distinct, region-dependent remodeling pattern in both NPY2R-positive and AC3-positive cilia. Ex vivo, direct NPY stimulation shortens endogenous NPY2R-positive primary cilia in hypothalamic slice cultures. In vitro, using a reconstituted human retinal pigment epithelial cell model expressing ciliary NPY2R, we found that this structural retraction was time-dependent, highly ligand-sensitive, reversible, and mediated by Gi/o-dependent Akt/JNK signaling. Notably, NPY-induced ciliary shortening and the reduction in NPY2R-positive cilia-bearing cells showed different sensitivities to Akt/JNK inhibition. Collectively, these findings demonstrate that NPY can directly remodel endogenous receptor-defined primary cilia and suggest that the ligand-driven structural plasticity of NPY2R-positive cilia may contribute to the tuning of hypothalamic signaling in response to changing nutritional conditions.