The coat protein complex II (COPII) mediates the sorting and export of cargo proteins from the endoplasmic reticulum (ER). We combine well-defined in vitro experimental systems that reconstitute COPII activities on ER membranes and liposomes, with cellular studies to provide a mechanistic view of the COPII-mediated ER export event.
In aim 1 of the studies, we will examine the hypothesis that GTPase regulated dissociation of Sar1 from constricted membranes destabilizes vesicle necks to mediate COPII-vesicle fission. We will monitor the activity of purified COPII proteins on defined liposomes to examine the fission event.
In aim 2 of the studies, we will examine the hypothesis that Sar1 assembly on the membrane regulates fission, and further explore the role of Sar1-induced membrane perturbation in the activation of lipid processing enzymes as a mechanism that couple lipid remodeling with vesicle formation. Structure-function studies on Sar1 will define the basis for the activity of Sar1 on membranes using liposomes and the information will be utilized in cellular models that recapitulate the synchronized export of different cargo proteins from the ER.
In aim 3 we will define the molecular basis for lipid-binding specificities of COPII-interacting proteins, using defined liposomes and ER membranes. Cellular studies will complement the analysis to define the role of selective lipid recognition in supporting the nucleation of COPII at defined ER exit sites. Importantly, a large number of human diseases are derived from mistakes in protein sorting at the ER. Developing mechanistic understanding of the molecular basis for COPII functions in ER export should enable the development of future effective therapeutics
The endoplasmic reticulum (ER) is a sub cellular compartment that functions as an assembly factory for proteins that are expressed on the cell surface or secreted from the cell. About a third of the proteins encoded by the human genome are assembled in the ER. Many seemingly unrelated human diseases are derived from mistakes in the shipment of assembled proteins from the ER. In our studies we explore the role of proteins that mediate this critical selection and shipment step. Specific proteins assemble the vesicles in which proteins to be shipped are selectively packaged. We reconstitute the vesicle formation process with pure proteins in a cell- free test tube settings. Experiments in this highly defined system provide insights that are than utilized for analysis in cells. Developing mechanistic understanding of the molecular basis for protein selection and export from the ER should enable the development of future effective therapeutics
| Long, Kimberly R; Yamamoto, Yasunori; Baker, Adam L et al. (2010) Sar1 assembly regulates membrane constriction and ER export. J Cell Biol 190:115-28 |
| Aridor, Meir; Fish, Kenneth N (2009) Selective targeting of ER exit sites supports axon development. Traffic 10:1669-84 |
| Schmidt, Béla Z; Watts, Rebecca J; Aridor, Meir et al. (2009) Cysteine string protein promotes proteasomal degradation of the cystic fibrosis transmembrane conductance regulator (CFTR) by increasing its interaction with the C terminus of Hsp70-interacting protein and promoting CFTR ubiquitylation. J Biol Chem 284:4168-78 |
