Plasma membrane localization and fusion inhibitory activity of the cowpox virus serpin SPI-3 require a functional signal sequence and the virus encoded hemagglutinin.
The cowpox virus (CPV) glycoprotein serpin SPI-3, a functional protease inhibitor, and the viral hemagglutinin (HA) are required to prevent fusion of wt CPV infected cells. SPI-3 and HA from CPV infected cells co-localize to the plasma membrane and are found in extracellular enveloped virus (EEV). We also show that an N-terminal SPI-3 signal sequence, but not glycosylation, is required for membrane localization and fusion inhibition. In the absence of HA (CPVDeltaHA), no SPI-3 is found on the membrane and infected cells fuse. Conversely, HA from both wt CPV and CPVDeltaSPI-3 infections is on the membrane, indicating a requirement of HA for SPI-3 plasma membrane localization. In the absence of HA, secretion of SPI-3 or SPI-3 N-glyc(-) was markedly enhanced, suggesting HA serves to retain SPI-3 on the plasma membrane,thereby preventing cell fusion.
Brum
Lauren M
LM
Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA.
Turner
Peter C
PC
Devick
Heather
H
Baquero
M Teresa
MT
Moyer
Richard W
RW
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D002462:Cell Membrane / Q000821:virology; D002522:Chlorocebus aethiops; D015608:Cowpox virus / Q000235:genetics / Q000502:physiology*; D004279:DNA, Viral / Q000235:genetics; D006031:Glycosylation; D006389:Hemagglutinins, Viral / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D008561:Membrane Fusion / Q000235:genetics / Q000502:physiology; D016297:Mutagenesis, Site-Directed; D021382:Protein Sorting Signals / Q000235:genetics / Q000502:physiology; D011995:Recombination, Genetic; D015843:Serpins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*
D004279:DNA, Viral; D006389:Hemagglutinins, Viral; D021382:Protein Sorting Signals; D015843:Serpins; D014764:Viral Proteins