Molecular Mechanism of Magnesium Transport in Neuronal Homeostasis

Magnesium (Mg2+) is essential for brain and nervous system health, playing critical roles in neuronal excitability, synaptic transmission, and protection against excitotoxicity. Disruptions in Mg2+ homeostasis— particularly chronic hypomagnesemia—are associated neurological disorders such as epilepsy, developmental delay, and neurodegeneration. The CNNM (Cyclin and CBS Domain Magnesium Transport Mediator) family of membrane proteins plays a central role in maintaining cellular and systemic Mg2+ balance. Mutations or dysfunctions in CNNMs are linked to severe neurological phenotypes, underscoring their importance in nervous system function. The CNNM family includes four members (CNNM1–4), each with distinct tissue distribution and physiological roles. These evolutionarily conserved proteins mediate Mg2+ efflux from cells, thereby regulating Mg2+ homeostasis critical for neuronal signaling and synaptic function. Despite their neurological relevance, the molecular architecture and transport mechanism of full-length CNNMs remain entirely unknown. Fundamental questions persist regarding how CNNMs recognize MgATP, undergo conformational changes to mediate Mg2+ efflux, and couple these processes to dynamic intracellular domains. Additionally, CNNM activity is modulated by small-molecule compounds and regulatory proteins such as PRLs (Phosphatases of Regenerating Liver) and ARL15 (ADP-Ribosylation Factor-Like GTPase 15), but how these factors alter transporter structure and function at the molecular level is poorly understood. We propose to define the structure and transport mechanism of CNNMs by integrating high-resolution cryo- electron microscopy with biochemical and functional assays. These studies will reveal how CNNMs transition through distinct functional states, how they sense intracellular Mg2+ levels, and how allosteric regulators— including small-molecule compounds and regulatory proteins—modulate their activity. The results will establish a comprehensive molecular framework for CNNM-mediated Mg2+ homeostasis and provide the foundation for future therapeutic strategies targeting magnesium-related neurological disorders. Project Number: 1R01NS149623-01 | Fiscal Year: 2026 | NIH Institute/Center: National Institute of Neurological Disorders and Stroke (NINDS) | Principal Investigator: Juan Du (+1 co-PI) | Institution: NORTHWESTERN UNIVERSITY, CHICAGO, IL | Award Amount: $630,651 | Activity Code: R01 | Study Section: Special Emphasis Panel[ZRG1 MBBC-Q (80)] View on NIH RePORTER: https://reporter.nih.gov/project-details/11389152