Interaction of Rab31 and OCRL‐1 in oligodendrocytes: Its role in transport of mannose 6‐phosphate receptors

Abstract

Rab31, a protein that we cloned from an oligodendrocyte cDNA library, is required for transport of mannose 6-phosphate receptors (MPRs) from the TGN to endosomes and for the Golgi/TGN organization. Here we extend the knowledge of the mechanism of action of Rab31 by demonstrating its interaction with OCRL-1, a phosphatidylinositol 4, 5 diphosphate 5-phosphatase (PI(4,5)P2 5-phosphatase) that regulates the levels of PI(4,5)P2 and PI(4)P, molecules involved in transport and Golgi/TGN organization. We show that Rab31 interacts with OCRL-1 by yeast two hybrid system, GST-Rab31 pull-down experiments and coimmunoprecipitation of OCRL-1 using oligodendrocyte culture lysates. Rab31 and OCRL-1 colocalize in the TGN, post TGN carriers and endosomes. Cation-dependent-MPR (CD-MPR) is sorted to OCRL-1-containing carriers, but CD63 and vesicular stomatitis virus G (VSVG) are not. siRNA-mediated depletion of endogenous Rab31 causes collapse of the TGN apparatus and markedly decreases the levels of OCRL-1 in the TGN and endosomes. Our observations indicate that the role of Rab31 in the Golgi/TGN structure and transport of MPRs depends on its capability to recruit OCRL-1 to domains of the TGN where the formation of carriers occurs. The importance of our observations is highlighted by the fact that mutation of OCRL-1 causes demyelination in humans.

Annexin A2 binds to endosomes following organelle destabilization by particulate wear debris

“…Cells were imaged every 20 min for 3 h. At least 40 cells were analysed per each experimental condition. Images were processed as described above 40 .…”

Bidirectional traffic between the Golgi and the endosomes – machineries and regulation

“…Rab31 interacts with Lowe oculocerebrorenal syndrome protein (OCRL) in oligodendrocytes (Rodriguez-Gabin et al, 2010). OCRL is a phosphatidylinositol 4,5-biphosphate [PtdIns(4,5)P 2 ] 5-phosphatase, which regulates the levels of PtdIns(4,5)P 2 and phosphatidylinositol 4-phosphate [PtdIns(4)P], both lipids involved in vesicular transport at the Golgi (Suchy et al, 1995).…”

The role of the small GTPase Rab31 in cancer

“…Larocca and colleagues first showed that Rab31 transcripts are enriched in brain oligodendrocytes, and demonstrated by video microscopy that Rab31 prominently labels tubulovesicular carrier structures originating from the trans-Golgi [ 82 ], and that Rab31 regulates transport of the cation-dependent mannose 6-phosphate receptor (CD-M6PR) from the Golgi to the endosome [ 86 ]. The authors also showed that Rab31 interacts with the Lowe oculocerebrorenal syndrome protein OCRL-1 (an Inositol polyphosphate 5-phosphatase) and that this interaction is required for trans-Golgi network (TGN) organization and transport carrier formation [ 87 ].…”