title: Two-pore channels form homo- and heterodimers.
abstract: Two-pore channels (TPCs) have been recently identified as NAADP-regulated Ca(2+) release channels, which are localized on the endolysosomal system. TPCs have a 12-transmembrane domain (TMD) structure and are evolutionary intermediates between the 24-TMD α-subunits of Na(+) or Ca(2+) channels and the transient receptor potential channel superfamily, which have six TMDs in a single subunit and form tetramers with 24 TMDs as active channels. Based on this relationship, it is predicted that TPCs dimerize to form functional channels, but the dimerization of human TPCs has so far not been studied. Using co-immunoprecipitation studies and a mass spectroscopic analysis of the immunocomplex, we show the presence of homo- and heteromeric complexes for human TPC1 and TPC2. Despite their largely distinct localization, we identified a discrete number of endosomes that coexpressed TPC1 and TPC2. Homo- and heteromerization were confirmed by a FRET study, showing that both proteins interacted in a rotational (N- to C-terminal/head-to-tail) symmetry. This is the first report describing the presence of homomultimeric TPC1 channels and the first study showing that TPCs are capable of forming heteromers.
authors: Department of Pharmacology, Oxford University, Oxford OX1 3QT, UK.
authors: Katja
authors: K
authors: Rietdorf
authors: Tim M
authors: TM
authors: Funnell
authors: Margarida
authors: M
authors: Ruas
authors: Jennifer
authors: J
authors: Heinemann
authors: John
authors: J
authors: Parrington
authors: Antony
authors: A
authors: Galione
mesh_terms: D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D009249:NADP / Q000031:analogs & derivatives / Q000378:metabolism; D055503:Protein Multimerization / Q000502:physiology*; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D000097903:Two-Pore Channels
chemical_list: D002118:Calcium; D015220:Calcium Channels; D009249:NADP; C407357:TPCN1 protein, human; D000097903:Two-Pore Channels; C530224:TPCN2 protein, human; C024376:NAADP