Photoreceptor IFT Complexes Containing Chaperones, Guanylyl Cyclase 1 and Rhodopsin |
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| Authors: | Reshma Bhowmick Mei Li Jun Sun Sheila A Baker Christine Insinna Joseph C Besharse |
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| Institution: | Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA; Current address: Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Current address: Fermentation Research Facility, E.I. du Pont de Nemours and Company, 2309 Sunset Lake Road, Newark, DE 19702, USA; Current address: Department of Ophthalmology, Duke University, Durham, NC 27710, USA |
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| Abstract: | Intraflagellar transport (IFT) provides a mechanism for the transport of cilium-specific proteins, but the mechanisms for linkage of cargo and IFT proteins have not been identified. Using the sensory outer segments (OS) of photoreceptors, which are derived from sensory cilia, we have identified IFT–cargo complexes containing IFT proteins, kinesin 2 family proteins, two photoreceptor-specific membrane proteins, guanylyl cyclase 1 (GC1, Gucy2e) and rhodopsin (RHO), and the chaperones, mammalian relative of DNAJ, DnajB6 (MRJ), and HSC70 (Hspa8). Analysis of these complexes leads to a model in which MRJ through its binding to IFT88 and GC1 plays a critical role in formation or stabilization of the IFT–cargo complexes. Consistent with the function of MRJ in the activation of HSC70 ATPase activity, Mg-ATP enhances the co-IP of GC1, RHO, and MRJ with IFT proteins. Furthermore, RNAi knockdown of MRJ in IMCD3 cells expressing GC1-green fluorescent protein (GFP) reduces cilium membrane targeting of GC1-GFP without apparent effect on cilium elongation. |
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| Keywords: | Cilium kinesin 2 HSC70 membrane guanylyl cyclase photoreceptor rhodopsin MRJ IFT |
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