Amiloride-sensitive Na channels.

The emerging epithelial Na channel/degenerin family of sodium channels is rapidly expanding, in particular with new members expressed in mammalian neurons and potentially involved in pain transmission. Experimental evidence supports a four-subunit stoichiometry for these channels (although this is still controversial), and basic functional elements (pore and selectivity filter, amiloride binding site, gating) have started to be attributed to specific domains of the protein. Although much remains to be done, in the past year progress has been made in the understanding of several regulatory mechanisms: the control of epithelial Na channel translation by mineralocorticoid hormones, the role of endocytosis and ubiquitination for degradation in the control of the channel density and the role of extracellular proteases.