title: A minimal isoform of the TMEM16A protein associated with chloride channel activity.
abstract: TMEM16A protein, also known as anoctamin-1, has been recently identified as an essential component of Ca(2+)-activated Cl(-) channels. We previously reported the existence of different TMEM16A isoforms generated by alternative splicing. In the present study, we have determined the functional properties of a minimal TMEM16A protein. This isoform, called TMEM16A(0), has a significantly shortened amino-terminus and lacks three alternative segments localized in the intracellular regions of the protein (total length: 840 amino acids). TMEM16A(0) expression is associated with Ca(2+)-activated Cl(-) channel activity as measured by three different functional assays based on the halide-sensitive yellow fluorescent protein, short-circuit current recordings, and patch-clamp technique. However, compared to a longer isoform, TMEM16(abc) (total length: 982 amino acids), TMEM16A(0) completely lacks voltage-dependent activation. Furthermore, TMEM16A(0) and TMEM16A(abc) have similar but not identical responses to extracellular anion replacement, thus suggesting a difference in ion selectivity and conductance. Our results indicate that TMEM16A(0) has the basic domains required for anion transport and Ca(2+)-sensitivity. However, the absence of alternative segments, which are present in more complex isoforms of TMEM16A, modifies the channel gating and ion transport ability.
authors.affiliation: Laboratorio di Genetica Molecolare, Largo Gerolamo Gaslini, Istituto Giannina Gaslini, 16147 Genova, Italy.
authors.forename: Loretta
authors.initials: L
authors.lastname: Ferrera
authors.forename: Paolo
authors.initials: P
authors.lastname: Scudieri
authors.forename: Elvira
authors.initials: E
authors.lastname: Sondo
authors.forename: Antonella
authors.initials: A
authors.lastname: Caputo
authors.forename: Emanuela
authors.initials: E
authors.lastname: Caci
authors.forename: Olga
authors.initials: O
authors.lastname: Zegarra-Moran
authors.forename: Roberto
authors.initials: R
authors.lastname: Ravazzolo
authors.forename: Luis J V
authors.initials: LJ
authors.lastname: Galietta
mesh_terms: D017398:Alternative Splicing; D000075369:Anoctamin-1; D001426:Bacterial Proteins / Q000378:metabolism; D002118:Calcium / Q000737:chemistry; D018118:Chloride Channels / Q000737:chemistry*; D002712:Chlorides / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D007477:Ions; D008164:Luminescent Proteins / Q000378:metabolism; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000737:chemistry*; D008856:Microscopy, Fluorescence / Q000379:methods; D009363:Neoplasm Proteins / Q000737:chemistry*; D018408:Patch-Clamp Techniques; D011487:Protein Conformation; D020033:Protein Isoforms; D014162:Transfection
chemical_list: C476213:ANO1 protein, human; D000075369:Anoctamin-1; D001426:Bacterial Proteins; D018118:Chloride Channels; D002712:Chlorides; D007477:Ions; D008164:Luminescent Proteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D020033:Protein Isoforms; C054562:yellow fluorescent protein, Bacteria; D002118:Calcium