TY  - GEN
ID  - heidok8437
KW  - LCMV 
KW  -  Signalpeptid 
KW  -  Glykoproteinreifung 
KW  -  Myristoylierung 
KW  -  TopologieER membrane insertion 
KW  -  stable signal peptide 
KW  -  LCMV 
KW  -  infectivity 
KW  -  glycoprotein maturation 
KW  -  topology
TI  - Functional Characterization of the LCMV GP-C Signal Peptide
Y1  - 2008///
AV  - public
N2  - N-terminal signal sequences of secretory and membrane proteins mediate targeting to and translocation across the endoplasmic reticulum (ER) membrane. After membrane insertion, signal sequences are in most cases cleaved from the precursor protein by signal peptidase (SPase). Signal sequences are usually 15 to 25 amino acid residues in length and have a typical tripartite structure with a central hydrophobic core of about 7 to 10 residues, a polar N-terminal region, and a short C-terminal region which contains the SPase cleavage site.  Insertion of the lymphocytic choriomeningitis virus (LCMV) precursor glycoprotein C (pGP-C) into the membrane of the ER is mediated by an unusual signal sequence. It comprises 58 amino acid residues and contains an extended N-terminal region including a myristoylation consensus site and two hydrophobic regions separated by a lysine residue. After cleavage by SPase, the resulting signal peptide (SPGP-C) accumulates in cells and virus particles. The aim of this study was to characterize the post-targeting functions of the LCMV SPGP-C. It could be shown that the LCMV SPGP-C is an essential component of the glycoprotein complex and that different regions of SPGP-C are required for distinct steps in glycoprotein maturation and virus infectivity. The investigation of SPGP-C deletion mutants showed that one hydrophobic region of LCMV SPGP-C is sufficient for ER membrane insertion of GP-C, while both hydrophobic regions are required for GP-C processing into its subunits and cell surface expression of the glycoprotein complex. The N-terminal region of SPGP-C and its myristoylation are dispensable for these steps in GP-C maturation, however, were found to be essential for viral infection of target cells. The analysis of a possible association of LCMV SPGP-C with GP-C by co-immunoprecipitation revealed that the LCMV SPGP-C is part of the glycoprotein complex and interacts with the membrane-anchored GP-2 subunit. For this non-covalent interaction the hydrophobic regions of SPGP-C are sufficient and essential, whereas the N-terminal region is not required. As the LCMV SPGP-C possesses two hydrophobic regions, different topologies across the membrane are conceivable. The membrane topology of SPGP-C was investigated using point mutations introducing potential N-glycosylation sites throughout the SPGP-C. It could be shown that unmyristoylated SPGP-C exposes its N-terminal region to the exoplasmic side of the membrane. This SPGP-C can promote GP-C maturation but is defective in viral infection. Myristoylation and SPGP-C membrane topology may thus hold the key to unravel the role of LCMV SPGP-C in GP-C complex assembly and function.
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/8437/
A1  - Schrempf, Sabrina
ER  -