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Identification of RanBP2‐ and Kinesin‐Mediated Transport Pathways with Restricted Neuronal and Subcellular Localization
Author(s) -
Mavlyutov Timur A.,
Cai Yunfei,
Ferreira Paulo A.
Publication year - 2002
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1034/j.1600-0854.2002.30905.x
Subject(s) - importin , microbiology and biotechnology , nuclear transport , biology , kinesin , nuclear pore , ran , nucleoporin , cytoplasm , transport protein , microtubule , cell nucleus
Ran‐binding proteins, karyopherins, and RanGTPase mediate and impart directionality to nucleocytoplasmic transport processes. This biological process remains elusive in neurons. RanBP2 has been localized at the nuclear pore complexes and is very abundant in the neuroretina. RanBP2 mediates the assembly of a large complex comprising RanGTPase, CRM1/exportin‐1, importin‐β, KIF5‐motor proteins, components of the 19S cap of the 26S proteasome, ubc9 and opsin. Here, we show RanBP2 is abundant in the ellipsoid compartment of photoreceptors and RanGTPase‐positive particles in cytoplasmic tracks extending away from the nuclear envelope of subpopulations of ganglion cells, suggesting RanBP2's release from nuclear pore complexes. KIF5C and KIF5B are specifically expressed in a subset of neuroretinal cells and differentially localize with RanBP2 and importin‐β in distinct compartments. The C‐terminal domains of KIF5B and KIF5C, but not KIF5A, associate directly with importin‐β in a RanGTPase‐dependent fashion in vivo and in vitro, indicating importin‐β is an endogenous cargo for a subset of KIF5s in retinal neurons. The KIF5 transport pathway is absent from the myoid region of a topographically distinct subclass of blue cones and the distribution of kinesin‐light chains is largely distinct from its KIF5 partners. Altogether, the results identify the existence of neuronal‐ and subtype‐specific kinesin‐mediated transport pathways of importin‐β‐bound cargoes to and/or from RanBP2 and indicate RanBP2 itself may also constitute a scaffold carrier for some of its associated partners. The implications of these findings in protein kinesis and pathogenesis of degenerative neuropathies are discussed.