Photoreceptor IFT complexes containing chaperones, guanylyl cyclase 1 and rhodopsin.
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.
Bhowmick
Reshma
R
Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Li
Mei
M
Sun
Jun
J
Baker
Sheila A
SA
Insinna
Christine
C
Besharse
Joseph C
JC
D000595:Amino Acid Sequence; D000818:Animals; D006162:Guanylate Cyclase / Q000378:metabolism*; D007150:Immunohistochemistry; D051379:Mice; D018832:Molecular Chaperones / Q000378:metabolism*; D008969:Molecular Sequence Data; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism*; D012243:Rhodopsin / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
D018832:Molecular Chaperones; D012243:Rhodopsin; D006162:Guanylate Cyclase