Identification of ciliary localization sequences within the third intracellular loop of G protein-coupled receptors.
Primary cilia are sensory organelles present on most mammalian cells. The functions of cilia are defined by the signaling proteins localized to the ciliary membrane. Certain G protein-coupled receptors (GPCRs), including somatostatin receptor 3 (Sstr3) and serotonin receptor 6 (Htr6), localize to cilia. As Sstr3 and Htr6 are the only somatostatin and serotonin receptor subtypes that localize to cilia, we hypothesized they contain ciliary localization sequences. To test this hypothesis we expressed chimeric receptors containing fragments of Sstr3 and Htr6 in the nonciliary receptors Sstr5 and Htr7, respectively, in ciliated cells. We found the third intracellular loop of Sstr3 or Htr6 is sufficient for ciliary localization. Comparison of these loops revealed a loose consensus sequence. To determine whether this consensus sequence predicts ciliary localization of other GPCRs, we compared it with the third intracellular loop of all human GPCRs. We identified the consensus sequence in melanin-concentrating hormone receptor 1 (Mchr1) and confirmed Mchr1 localizes to primary cilia in vitro and in vivo. Thus, we have identified a putative GPCR ciliary localization sequence and used this sequence to identify a novel ciliary GPCR. As Mchr1 mediates feeding behavior and metabolism, our results implicate ciliary signaling in the regulation of body weight.
Berbari
Nicolas F
NF
Department of Pharmacology, Division of Human Genetics, and College of Medicine, The Ohio State University, Columbus, OH 43210, USA.
Johnson
Andrew D
AD
Lewis
Jacqueline S
JS
Askwith
Candice C
CC
Mykytyn
Kirk
K
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D002923:Cilia / Q000378:metabolism*; D016384:Consensus Sequence; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D043562:Receptors, G-Protein-Coupled / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011985:Receptors, Serotonin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017481:Receptors, Somatostatin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
C103263:MCHR1 protein, human; D043562:Receptors, G-Protein-Coupled; D011985:Receptors, Serotonin; D017481:Receptors, Somatostatin; D011993:Recombinant Fusion Proteins; C485184:enhanced green fluorescent protein; C103631:somatostatin receptor 3; D049452:Green Fluorescent Proteins