title: Dynamics and Distribution of Klothoβ (KLB) and fibroblast growth factor receptor-1 (FGFR1) in living cells reveal the fibroblast growth factor-21 (FGF21)-induced receptor complex.
abstract: FGF21 stimulates FGFR1c activity in cells that co-express Klothoβ (KLB); however, relatively little is known about the interaction of these receptors at the plasma membrane. We measured the dynamics and distribution of fluorescent protein-tagged KLB and FGFR1c in living cells using fluorescence recovery after photobleaching and number and brightness analysis. We confirmed that fluorescent protein-tagged KLB translocates to the plasma membrane and is active when co-expressed with FGFR1c. FGF21-induced signaling was enhanced in cells treated with lactose, a competitive inhibitor of the galectin lattice, suggesting that lattice-binding modulates KLB and/or FGFR1c activity. Fluorescence recovery after photobleaching analysis consistently revealed that lactose treatment increased KLB mobility at the plasma membrane, but did not affect the mobility of FGFR1c. The association of endogenous KLB with the galectin lattice was also confirmed by co-immunoprecipitation with galectin-3. KLB mobility increased when co-expressed with FGFR1c, suggesting that the two receptors form a heterocomplex independent of the galectin lattice. Number and brightness analysis revealed that KLB and FGFR1c behave as monomers and dimers at the plasma membrane, respectively. Co-expression resulted in monomeric expression of KLB and FGFR1c consistent with formation of a 1:1 heterocomplex. Subsequent addition of FGF21 induced FGFR1 dimerization without changing KLB aggregate size, suggesting formation of a 1:2 KLB-FGFR1c signaling complex. Overall, these data suggest that KLB and FGFR1 form a 1:1 heterocomplex independent of the galectin lattice that transitions to a 1:2 complex upon the addition of FGF21.
authors.affiliation: Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3G9, Canada.
authors.forename: Aaron Y K
authors.initials: AY
authors.lastname: Ming
authors.forename: Eunjong
authors.initials: E
authors.lastname: Yoo
authors.forename: Eugene N
authors.initials: EN
authors.lastname: Vorontsov
authors.forename: Svetlana M
authors.initials: SM
authors.lastname: Altamentova
authors.forename: Dawn M
authors.initials: DM
authors.lastname: Kilkenny
authors.forename: Jonathan V
authors.initials: JV
authors.lastname: Rocheleau
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000378:metabolism*; D037502:Galectin 3 / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D000090265:Klotho Proteins; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D055503:Protein Multimerization / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D037502:Galectin 3; C418622:Klb protein, mouse; C485095:Lgals3 protein, mouse; D008565:Membrane Proteins; D046912:Multiprotein Complexes; C414620:fibroblast growth factor 21; D005346:Fibroblast Growth Factors; C496348:FGFR1 protein, human; C496349:Fgfr1 protein, mouse; D051496:Receptor, Fibroblast Growth Factor, Type 1; D000090265:Klotho Proteins