Reid Gilmore, Ph.D.

Academic Role: Professor

Faculty Appointment(s) In:
   Biochemistry and Molecular Pharmacology

Other Affiliation(s):
   Interdisciplinary Graduate Program

Molecular mechanism of secretory protein translocation

The objective of research in our laboratory is to understand how proteins reach their final destinations within a cell. Specifically, we are investigating the biosynthesis, translocation, processing and folding of proteins in the rough endoplasmic reticulum.

A major goal of our lab is to elucidate the mechanism of protein translocation across the rough endoplasmic reticulum (RER) membrane. The signal recognition particle (SRP), a ribonucleoprotein that binds to the polypeptide exit site on the ribosome, and the membrane bound SRP receptor (SR) function together to selectively attach a ribosome synthesizing a protein with an RER signal sequences to the Sec61 complex. The Sec61 heterotrimer forms an evolutionarily conserved channel for translocation of secreted proteins and integration of membrane proteins.    We are using the Saccharomyces cerevisiae experimental to analyze the mechanism of translocation channel gating by ribosome-nascent chain complexes.  Novel Sec61 mutants are designed based upon the structure of the Methanococcus janaschii SecYEb complex.   The in vivo kinetics of protein translocation channel gating are being analyzed using ubiquitin translocation assay (UTA) reporters.  

Asparagine-linked glycosylation of proteins occurs within the lumen of the RER. Oligosaccharyltransferase (OST) catalyzes the transfer of a preassembled high-mannose oligosaccharide onto N-X-T or N-X-S acceptor sites (seqons) as the nascent polypeptide is transported into the RER lumen through the Sec61 complex. The oligosaccharide donor for the enzyme is the dolichol pyrophosphate linked oligosaccharide GlcNAc₂Man₉Glc₃.    The oligosaccharyltransferase is a hetero-octameric integral membrane protein in higher eukaryotes.   Many unicellular protists have simpler OSTs with either a single subunit (e.g. Trypanosoma cruzi) or four subunits (e.g. Entamoeba histolytica).   The active site subunit of the OST is the STT3 protein.  Interestingly, the genomes of insects, plants and vertebrates encode two STT3 proteins. Biochemical experiments have revealed that the two SST3 proteins (STT3A and STT3B) assemble with a shared set of non-catalytic subunits into two separate OST complexes with different kinetic properties.   We are analyzing the roles of these two distinct OST complexes in tissue culture cells by selectively knocking down STT3A or STT3B expression using siRNAs.  Current evidence indicates that the STT3A isoform of the OST is primarily responsible for cotranslational glycosylation of nascent glycoproteins as the acceptor sequons exit the luminal face of the translocation channel.   The STT3B isoform of the OST can modify skipped sequons on unfolded proteins in the lumen of the ER. 

Publications - Reid Gilmore, PhD

Mandon, E.C., S.F. Trueman, and R. Gilmore. 2009. Translocation of proteins through the Sec61 and SecYEG channels. Curr. Opin. Cell. Biol. 21:501-507.

Ruiz-Canada, C., D.J. Kelleher, and R. Gilmore. 2009. Cotranslational and posttranslational N-glycosylation of polypeptides by distinct mammalian OST isoforms. Cell 136:272-283.

Jiang, Y., Z. Cheng, E.C. Mandon, and R. Gilmore. 2008. An interaction between the SRP receptor and the translocon is critical during cotranslational protein translocation. J. Cell. Biol. 180:1149-1161.

Kelleher, D.J., S. Banerjee, A.J. Cura, J. Samuelson, and R. Gilmore. 2007. Dolichol-linked oligosaccharide selection by the oligosaccharyltransferase in protist and fungal organisms. J. Cell Biol. 177:29-37.

Cheng, Z. and R. Gilmore. 2006. Slow translocon gating causes cytosolic exposure of transmembrane and lumenal domains during membrane protein integration. Nat. Struct. Mol. Biol. 13:930-936.

Kelleher, D.J. and R. Gilmore. 2006. An evolving view of the eukaryotic oligosaccharyltransferase. Glycobiology 16:47-62.

Samuelson, J., S. Banerjee, P. Magnelli, J. Cui, D.J. Kelleher, R. Gilmore, and P.W. Robbins. 2005. The diversity of dolichol-linked precursors to Asn-linked glycans likely results from secondary loss of sets of glycosyltransferases. Proc. Natl. Acad. Sci. USA 102:1548-1553.

Cheng, Z., Y. Jiang, E.C. Mandon, and R. Gilmore. 2005. Identification of cytoplasmic residues of Sec61p involved in ribosome binding and cotranslational translocation. J. Cell Biol. 168:67-77.

Mandon, E.C., Y. Jiang, and R. Gilmore. 2003. Dual recognition of the ribosome and the signal recognition particle by the SRP receptor during protein targeting to the endoplasmic reticulum. J. Cell Biol. 162:575-585.

Kelleher, D.J., D. Karaoglu, E.C. Mandon, and R. Gilmore. 2003. Oligosaccharyltransferase isoforms that contain different catalytic STT3 subunits have distinct enzymatic properties. Mol. Cell 12:101-111.

Nilsson, I., D.J. Kelleher, Y. Miao, Y. Shao, G. Kreibich, R. Gilmore, G. Von Heijne, and A.E. Johnson. 2003. Photocross-linking of nascent chains to the STT3 subunit of the oligosaccharyltransferase complex. J. Cell Biol. 161:715-725.

Karaoglu, D., D.J. Kelleher, and R. Gilmore. 2001. Allosteric regulation provides a molecular mechanism for preferential utilization of the fully assembled dolichol-linked oligosaccharide by the yeast oligosaccharyltransferase. Biochemistry 40:12193-12206.

Raden, D., W. Song, and R. Gilmore. 2000. Role of the cytoplasmic segments of Sec61alpha in the ribosome-binding and translocation-promoting activities of the Sec61 complex. J. Cell Biol. 150:53-64.

Song, W., D. Raden, E.C. Mandon, and R. Gilmore. 2000. Role of Sec61alpha in the regulated transfer of the ribosome-nascent chain complex from the signal recognition particle to the translocation channel. Cell 100:333-343.

Rotation Project Background

Laboratory Personnel

Research Associate Professor

Elisabet Mandon, Ph.D.

Graduate Student
         Steve Trueman 
         Amber Lachapelle

PhD, University of Illinois, Urbana, 1980
Postdoctoral Training
The Rockefeller University, 1980-1983

Office: Research 915, LAB N-P
Phone: 508-856-5894
Fax: 508-856-6231
E-mail: Reid.Gilmore@umassmed.edu
Keywords: Intracellular Trafficking, Clinical Research, Biochemistry

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