Noncanonical roles of voltage-gated sodium channels.

The Hodgkin-Huxley formulation, at its 60th anniversary, remains a bastion of neuroscience. Sodium channels Nav1.1-Nav1.3 and Nav1.6-Nav1.9 support electrogenesis in neurons and are often considered "neuronal," whereas Nav1.4 and Nav1.5 drive electrogenesis in skeletal and cardiac muscle. These channels are, however, expressed in cell types that are not considered electrically excitable. Here, we discuss sodium channel expression in diverse nonexcitable cell types, including astrocytes, NG2 cells, microglia, macrophages, and cancer cells, and review evidence of noncanonical roles, including regulation of effector functions such as phagocytosis, motility, Na(+)/K(+)-ATPase activity, and metastatic activity. Armed with powerful techniques for monitoring channel activity and for real-time assessment of [Na(+)]i and [Ca(2+)]i, neuroscientists are poised to expand the understanding of noncanonical roles of sodium channels in healthy and diseased tissues.