Alternate promoters and variable splicing lead to hNedd4-2 isoforms with a C2 domain and varying number of WW domains

Omar A. Itani, Jason R. Campbell, Juan Herrero, Peter M. Snyder, Christie P. Thomas

Research output: Contribution to journalArticlepeer-review

57 Scopus citations

Abstract

Mutations that disrupt a PY motif in epithelial Na+ channel (ENaC) subunits increase surface expression of Na+ channels in the collecting duct, resulting in greater Na+ reabsorption. Recently, Nedd4 and Nedd4-2 have been identified as ubiquitin ligases that can interact with ENaC via its PY motifs to regulate channel activity. To further understand the role of human Nedd4-2 (hNedd4-2), we cloned its cDNAs and determined its genomic organization using a bioinformatic approach. The gene is present as a single copy, spans at least 400 kb, and contains >40 exons. Multiple 5′-exons were identified by 5′-rapid amplification of cDNA ends, and tissue-specific expression of these transcripts was noted by RT-PCR and RNase protection assay. Alternate polyadenylation signal sequences led to varying lengths of the 3′-untranslated region. Alternate splicing events within internal exons were also noted. Open reading frame analysis indicates that hNedd4-2 encode multiple protein variants with and without a C2 domain, and with a variable number of WW domains. Coexpression, in Fischer rat thyroid epithelia, of ENaC and Nedd4-2 cDNAs leads to a significant reduction in amiloride-sensitive currents, confirming a role in Na+ transport regulation. In vitro binding studies demonstrated that individual PY motifs of α-, β-, and γ-ENaC have strong affinity for WW domains 3 and 4 but not 1 and 2. These studies indicate that alternate transcripts of Nedd4-2 may interact with ENaC differently. Understanding the function of variant proteins will increase our knowledge of the role of hNedd4-2 in the regulation of ENaC and define protein domains important for Nedd4-2 function.

Original languageEnglish
Pages (from-to)F916-F929
JournalAmerican Journal of Physiology - Renal Physiology
Volume285
Issue number5 54-5
DOIs
StatePublished - Nov 2003

Keywords

  • Epithelial sodium channel
  • Nedd4L
  • Sodium transport
  • Ubiquitin ligase

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