title: Functional multimerization of mucolipin channel proteins.
abstract: MCOLN1 encodes mucolipin-1 (TRPML1), a member of the transient receptor potential TRPML subfamily of channel proteins. Mutations in MCOLN1 cause mucolipidosis-type IV (MLIV), a lysosomal storage disorder characterized by severe neurologic, ophthalmologic, and gastrointestinal abnormalities. Along with TRPML1, there are two other TRPML family members, mucolipin-2 (TRPML2) and mucolipin-3 (TRPML3). In this study, we used immunocytochemical analysis to determine that TRPML1, TRPML2, and TRPML3 co-localize in cells. The multimerization of TRPML proteins was confirmed by co-immunoprecipitation and Western blot analysis, which demonstrated that TRPML1 homo-multimerizes as well as hetero-multimerizes with TRPML2 and TRPML3. MLIV-causing mutants of TRPML1 also interacted with wild-type TRPML1. Lipid bilayer re-constitution of in vitro translated TRPML2 and TRPML3 confirmed their cation channel properties with lower single channel conductance and higher partial permeability to anions as compared to TRPML1. We further analyzed the electrophysiological properties of single channel TRPML hetero-multimers, which displayed functional differences when compared to individual TRPMLs. Our data shows for the first time that TRPMLs form distinct functional channel complexes. Homo- and hetero-multimerization of TRPMLs may modulate channel function and biophysical properties, thereby increasing TRPML functional diversity.
authors.affiliation: Center for Human Genetic Research, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
authors.forename: Cyntia
authors.initials: C
authors.lastname: Curcio-Morelli
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.forename: Bhuvarahamurthy
authors.initials: B
authors.lastname: Venugopal
authors.forename: Florie A
authors.initials: FA
authors.lastname: Charles
authors.forename: Marsha F
authors.initials: MF
authors.lastname: Browning
authors.forename: Horacio F
authors.initials: HF
authors.lastname: Cantiello
authors.forename: Susan A
authors.initials: SA
authors.lastname: Slaugenhaupt
mesh_terms: D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D002463:Cell Membrane Permeability; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D008564:Membrane Potentials; D009154:Mutation; D011485:Protein Binding; D055503:Protein Multimerization; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D050053:TRPM Cation Channels / Q000378:metabolism; D014162:Transfection; D050051:Transient Receptor Potential Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: C416674:MCOLN1 protein, human; C510642:MCOLN3 protein, human; C510641:Mcoln2 protein, human; D011993:Recombinant Fusion Proteins; D050053:TRPM Cation Channels; D050051:Transient Receptor Potential Channels