• Corpus ID: 14709886

Functional characterisation of Rab22a and Munc18b, two proteins regulating vesicle transport in mammalian cells

  title={Functional characterisation of Rab22a and Munc18b, two proteins regulating vesicle transport in mammalian cells},
  author={Maria Kauppi},
V SUMMARY AND CONCLUSIONS 59 VI ACKNOWLEDGEMENTS 62 VII REFERENCES 63 5 ORIGINAL PUBLICATIONS This thesis is based on the following articles, which are in the text referred to their Roman numerals. In addition, some unpublished results are presented. (2001) The small GTPase Rab22 interacts with EEA1 and controls endosomal membrane trafficking. (2000) Munc18-2, a functional partner of syntaxin 3, controls apical membrane trafficking in epithelial cells. (2002) Analysis of the Munc18b-syntaxin… 



Rab 7: an important regulator of late endocytic membrane traffic

A key role for rab7, downstream of rab5, in regulating membrane transport leading from early to late endosomes is supported, and horseradish peroxidase and SV5 hemagglutinin-neuraminidase were used in quantitative biochemical assays to demonstrate that rab7 function was not required for early internalization events, but was crucial in downstream degradative events.

Regulation of Exocytosis by Cyclin-dependent Kinase 5 via Phosphorylation of Munc18*

The data suggest a model whereby Cdk5 acts to regulate Munc18a interaction with syntaxin 1a and thereby modulates the level of vesicle SNARE interaction withntaxin 1 a and secretory responsiveness.

A sec1-related vesicle-transport protein that is expressed predominantly in epithelial cells.

The cloning and molecular characterization of a Sec1-related protein expressed in the MDCK epithelial cell line is reported, identifying Munc-18-2 as a predominantly epithelial vesicle-transport protein with a polarized distribution and provided novel in vivo evidence for the association of Sec 1-related proteins with members of the syntaxin family.

Inhibition of rab5 GTPase activity stimulates membrane fusion in endocytosis.

The opposite effects of the rab5 Q79L and S34N mutants suggest that rab5:GTP is required prior to membrane fusion, whereas GTP hydrolysis by rab5 occurs after membrane fusion and functions to inactivate the protein.

Rab9 functions in transport between late endosomes and the trans Golgi network.

The results strongly suggest that rab9 functions in the transport of mannose 6‐phosphate receptors between late endosomes and the trans Golgi network, and confirm the observation that a given organelle may bear multiple rab proteins with different biological functions.

Requirement of nucleotide exchange factor for Ypt1 GTPase mediated protein transport

The results suggest that the dominant mutant proteins inhibit protein transport by sequestering the exchange factor from the wild type Ypt1 protein, and that this factor has an essential role in vesicular transport.

Munc18 Interacting Proteins

MINTs are a family of Arf-dependent, vesicle-coat proteins that can regulate the traffic of β-APP, and it is demonstrated that MINTs bind Arfs directly, co-localize with Arf and the Alzheimer's precursor protein (β-APP), and can co-immunoprecipitate clathrin.

The rab7 GTPase resides on a vesicular compartment connected to lysosomes.

The data implicate rab7 as the first GTPase functioning on terminal endocytic structures in mammalian cells and observe that, in contrast to the wild-type protein, a rab7 mutant with a reduced GTP enzyme activity is in part associated with lysosomal membranes.

Phosphorylation of Munc-18/n-Sec1/rbSec1 by Protein Kinase C

It is shown that recombinant Munc-18 is phosphorylated by conventional PKC in a Ca- and phospholipid-dependent manner in a cell-free system and this results suggest that the PKC-catalyzed phosphorylation of Munm-18 plays an important role in regulating the interaction of MunC-18 with syntaxin and thereby the docking and/or the fusion of synaptic vesicles with the presynaptic plasma membrane.

Rab1 Interaction with a GM130 Effector Complex Regulates COPII Vesicle cis‐Golgi Tethering

This work demonstrates that the cis‐Golgi tethering protein GM130, complexed with GRASP65 and other proteins, forms a novel Rab1 effector complex that interacts with activated Rab1‐GTP in a p115‐independent manner and is required for coat protein II vesicle targeting/fusion with the cis-golgi.