title: Atomic force microscopy reveals the alternating subunit arrangement of the TRPP2-TRPV4 heterotetramer.
abstract: There is evidence that polycystin-2 (TRPP2) interacts with two other members of the transient receptor potential (TRP) family, TRPC1 and TRPV4. We have previously shown that TRPP2 forms a heteromeric complex with TRPC1, with a 2:2 stoichiometry and an alternating subunit arrangement. Here, we used coimmunoprecipitation to show that TRPP2 also interacts with TRPV4, but not with TRPA1 or TRPM8; hence, its promiscuity is limited. We then used atomic force microscopy to study the structure of the TRPV4 homomer and the interaction between TRPP2 and TRPV4. The molecular volume of V5-tagged TRPV4 isolated from singly-transfected tsA 201 cells indicated that it assembled as a homotetramer. The distribution of angles between pairs of anti-V5 antibodies bound to TRPV4 particles had a large peak close to 90 degrees and a smaller peak close to 180 degrees , again consistent with the assembly of TRPV4 as a homotetramer. In contrast, the angle distributions for decoration of the TRPP2-TRPV4 heteromer by either anti-Myc or anti-V5 antibodies had major peaks close to 180 degrees. This result indicates that TRPP2-TRPV4 assembles identically to TRPP2-TRPC1, suggesting a common subunit arrangement among heteromeric TRP channels.
authors.affiliation: Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Stewart
authors.forename: Graham D
authors.initials: GD
authors.lastname: Smith
authors.forename: Richard N
authors.initials: RN
authors.lastname: Sandford
authors.forename: J Michael
authors.initials: JM
authors.lastname: Edwardson
mesh_terms: D000818:Animals; D002460:Cell Line; D006801:Humans; D047468:Immunoprecipitation; D051379:Mice; D018625:Microscopy, Atomic Force; D055503:Protein Multimerization; D021122:Protein Subunits / Q000378:metabolism*; D051381:Rats; D050396:TRPP Cation Channels / Q000302:isolation & purification / Q000378:metabolism*; D050916:TRPV Cation Channels / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D021122:Protein Subunits; D050396:TRPP Cation Channels; D050916:TRPV Cation Channels; C486576:Trpv4 protein, mouse