title: Scaffold protein connector enhancer of kinase suppressor of Ras isoform 3 (CNK3) coordinates assembly of a multiprotein epithelial sodium channel (ENaC)-regulatory complex.
abstract: Hormone regulation of ion transport in the kidney tubules is essential for fluid and electrolyte homeostasis in vertebrates. A large body of evidence has suggested that transporters and channels exist in multiprotein regulatory complexes; however, relatively little is known about the composition of these complexes or their assembly. The epithelial sodium channel (ENaC) in particular is tightly regulated by the salt-regulatory hormone aldosterone, which acts at least in part by increasing expression of the serine-threonine kinase SGK1. Here we show that aldosterone induces the formation of a 1.0-1.2-MDa plasma membrane complex, which includes ENaC, SGK1, and the ENaC inhibitor Nedd4-2, a key target of SGK1. We further show that this complex contains the PDZ domain-containing protein connector enhancer of kinase suppressor of Ras isoform 3 (CNK3). CNK3 physically interacts with ENaC, Nedd4-2, and SGK1; enhances the interactions among them; and stimulates ENaC function in a PDZ domain-dependent, aldosterone-induced manner. These results strongly suggest that CNK3 is a molecular scaffold, which coordinates the assembly of a multiprotein ENaC-regulatory complex and hence plays a central role in Na(+) homeostasis.
authors.affiliation: Division of Nephrology, Department of Medicine, University of California, San Francisco, California 94143, USA.
authors.forename: Rama
authors.initials: R
authors.lastname: Soundararajan
authors.forename: Tim
authors.initials: T
authors.lastname: Ziera
authors.forename: Eric
authors.initials: E
authors.lastname: Koo
authors.forename: Karen
authors.initials: K
authors.lastname: Ling
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.forename: Steffen A
authors.initials: SA
authors.lastname: Borden
authors.forename: David
authors.initials: D
authors.lastname: Pearce
mesh_terms: D000450:Aldosterone / Q000494:pharmacology; D000818:Animals; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism*; D053503:Epithelial Sodium Channels / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D000075702:Nedd4 Ubiquitin Protein Ligases; D054731:PDZ Domains; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D000099184:Serum-Glucocorticoid Regulated Kinases
chemical_list: D000450:Aldosterone; D056827:Endosomal Sorting Complexes Required for Transport; D053503:Epithelial Sodium Channels; D017874:Immediate-Early Proteins; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D000075702:Nedd4 Ubiquitin Protein Ligases; D017346:Protein Serine-Threonine Kinases; D012964:Sodium; D044767:Ubiquitin-Protein Ligases; D000099184:Serum-Glucocorticoid Regulated Kinases; C496471:CNKSR3 protein, human; C000618483:Nedd4 protein, human; C000618485:Nedd4L protein, human; C000618461:Nedd4l protein, mouse