title: Vesicular transport of a ribonucleoprotein to mitochondria.
abstract: Intracellular trafficking of viruses and proteins commonly occurs via the early endosome in a process involving Rab5. The RNA Import Complex (RIC)-RNA complex is taken up by mammalian cells and targeted to mitochondria. Through RNA interference, it was shown that mito-targeting of the ribonucleoprotein (RNP) was dependent on caveolin 1 (Cav1), dynamin 2, Filamin A and NSF. Although a minor fraction of the RNP was transported to endosomes in a Rab5-dependent manner, mito-targeting was independent of Rab5 or other endosomal proteins, suggesting that endosomal uptake and mito-targeting occur independently. Sequential immunoprecipitation of the cytosolic vesicles showed the sorting of the RNP away from Cav1 in a process that was independent of the endosomal effector EEA1 but sensitive to nocodazole. However, the RNP was in two types of vesicle with or without Cav1, with membrane-bound, asymmetrically orientated RIC and entrapped RNA, but no endosomal components, suggesting vesicular sorting rather than escape of free RNP from endosomes. In vitro, RNP was directly transferred from the Type 2 vesicles to mitochondria. Live-cell imaging captured spherical Cav1(-) RNP vesicles emerging from the fission of large Cav(+) particles. Thus, RNP appears to traffic by a different route than the classical Rab5-dependent pathway of viral transport.
authors.affiliation: Genetic Engineering Laboratory, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Calcutta 700032, India Present address: Penn Institute for Regenerative Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104, USA.
authors.forename: Joyita
authors.initials: J
authors.lastname: Mukherjee
authors.affiliation: Present address: Penn Institute for Regenerative Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104, USA.
authors.forename: Biraj
authors.initials: B
authors.lastname: Mahato
authors.affiliation: Genetic Engineering Laboratory, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Calcutta 700032, India Present address: Penn Institute for Regenerative Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104, USA. nilugrandson@gmail.com.
authors.forename: Samit
authors.initials: S
authors.lastname: Adhya
keywords: Caveolin 1; Endosome; Mitochondria; RNA protein complex; Sorting