This study aims to explore the molecular mechanisms, physiological functional significance, disease and therapeutic relevance of a radically new neuron-like function of the understudied but chief renal cell type of the macula densa (MD). MD cells are traditionally known as specialized renal epithelial cells capable of sensing the local tissue environment and releasing various chemical messengers to control renal and glomerular hemodynamics via tubuloglomerular feedback, and renin release as their classic functions. In addition, our work in the last grant cycle identified their novel function in endogenous kidney tissue remodeling and repair. However, interesting new insights suggest neuron-like function of these cells. Preliminary work using unbiased intravital multiphoton microscopy (MPM) of MD versus all other renal cell calcium responses uncovered neuron-like rapid and regularly oscillating spontaneous calcium transients (pacemaker activity), coordinated cell-to-cell propagation within the MD via long (>50 µm), axon-like cell processes that were entirely specific to MD cells. Numerous neurotransmitters and systemic neuroendocrine hormones given locally or iv triggered robust and specific MD cell calcium responses and increased afferent renal nerve activity. MD cell gene profile and tissue enrichment analysis identified brain tissue specificity of MD cells, and the expression of numerous neuronal markers including nerve growth factor receptor p75NTR (NGFR, the highest expressed growth factor receptor in MD cells), and some of the major Alzheimer’s disease risk genes. These studies painted a paradigm-shifting new picture of MD cells functioning as interoceptive neuron-like cells that form autonomous, nephron-level neuronal networks in the kidney, sense the local and systemic environment, process and send signals to renal and central effectors in the brain to maintain homeostasis. Our central hypothesis is that neuron-like MD cell calcium and NGFR signaling play novel primary roles in physiological responses to control renal hemodynamics, renin, and tissue remodeling (local interoception) and whole body homeostasis (systemic interoception). Further, we hypothesize that alterations in the neuron-like functions of MD cells represent a novel, neurodegenerative component in the pathogenesis of chronic kidney disease (CKD) and can be therapeutically targeted. This project will use comprehensive experimental approaches including new transgenic mice with chemo and optogenetic tools, in vivo MPM imaging including innovative 3-photon excitation, MD transcriptome analysis, bioinformatics, in vitro MD cell culturing and models of CKD. The specific aims are to examine the role of MD cell neuron-like calcium and NGFR signaling in (1) physiological responses of the JGA, (2) in the development and progression of kidney disease, and (3) their therapeutic potential in CKD. These novel MD cell-specific molecular and signaling mechanisms may be targeted in the futu...