Abstract
Dysfunctional trafficking to primary cilia is a frequent cause of human diseases known as ciliopathies, yet molecular mechanisms for specific targeting of sensory receptors to cilia are largely unknown. Here, we show that the targeting of ciliary cargo, represented by rhodopsin, is mediated by a specialized system, the principal component of which is the Arf GAP ASAP1. Ablation of ASAP1 abolishes ciliary targeting and causes formation of actin-rich periciliary membrane projections that accumulate mislocalized rhodopsin. We find that ASAP1 serves as a scaffold that brings together the proteins necessary for transport to the cilia including the GTP-binding protein Arf4 and the two G proteins of the Rab family--Rab11 and Rab8--linked by the Rab8 guanine nucleotide exchange factor Rabin8. ASAP1 recognizes the FR ciliary targeting signal of rhodopsin. Rhodopsin FR-AA mutant, defective in ASAP1 binding, fails to interact with Rab8 and translocate across the periciliary diffusion barrier. Our study implies that other rhodopsin-like sensory receptors may interact with this conserved system and reach the cilia using the same platform.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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ADP-Ribosylation Factors / physiology*
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Adaptor Proteins, Signal Transducing / antagonists & inhibitors
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Adaptor Proteins, Signal Transducing / genetics
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Adaptor Proteins, Signal Transducing / physiology*
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Animals
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Cattle
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Cells, Cultured
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Cilia / physiology*
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Epithelial Cells / metabolism
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Epithelial Cells / ultrastructure
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Germinal Center Kinases
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Golgi Apparatus / metabolism
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Kidney Tubules, Collecting / cytology
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Mice
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Mice, Knockout
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Models, Molecular
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Photoreceptor Connecting Cilium / physiology
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Protein Binding
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Protein Interaction Mapping
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Protein Serine-Threonine Kinases / physiology*
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Protein Transport
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RNA Interference
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RNA, Small Interfering / pharmacology
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Ranidae
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Recombinant Fusion Proteins / metabolism
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Retinal Photoreceptor Cell Outer Segment
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Rhodopsin / chemistry
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Rhodopsin / genetics
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Rhodopsin / metabolism
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Rod Cell Outer Segment / physiology*
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Rod Cell Outer Segment / ultrastructure
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rab GTP-Binding Proteins / physiology*
Substances
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Adaptor Proteins, Signal Transducing
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Asap1 protein, mouse
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Germinal Center Kinases
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RNA, Small Interfering
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Rab8 protein, mouse
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Recombinant Fusion Proteins
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Rhodopsin
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Protein Serine-Threonine Kinases
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rab11 protein
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ADP-Ribosylation Factors
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ARF4 protein, mouse
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rab GTP-Binding Proteins