Structure and Replication of Influenza Virus 
and Paramyxoviruses 
Robert A. Lamb, Ph.D. — Investigator 
Dr. Lamb is also John Evans Professor of Molecular and Cellular Biology and Professor of 
Microbiology-Immunology at Northwestern University. He received his undergraduate degree reading 
biochemistry at the University of Birmingham, England, and his Ph.D. degree from the University of 
Cambridge. He came to the United States to do postdoctoral work with Purnell Choppin at the Rockefeller 
University, where he later became a faculty member. Nine years ago he joined the faculty of Northwestern 
University. 
ANIMAL viruses provide a unique tool w^ith 
which to increase understanding of the com- 
plex biochemical processes involved in the bio- 
synthesis and maintenance of eukaryotic cells. 
Our laboratory is investigating the molecular 
structure and the mechanism of replication of 
two enveloped viruses, influenza virus and the 
paramyxovirus SV5 . 
Influenza virus causes important diseases in 
humans and animals. It has tremendous socioeco- 
nomic consequences, because influenza contin- 
ues to occur in regular epidemics and occasional 
pandemics and is a leading cause of morbidity 
and mortality. Paramyxoviruses cause many bio- 
logically and economically important diseases. 
Among these viruses are parainfluenza types 1-5, 
mumps, measles, canine distemper, Newcastle 
disease of chickens, and rinderpest of cattle, as 
well as SV5. 
We are elucidating the wide range of mecha- 
nisms that these RNA viruses use to maximize the 
encoded proteins in their compact genomes. We 
have identified overlapping reading frames, 
splicing of mRNAs, the use of bicistronic mRNAs, 
transcriptional stuttering to add nontemplated 
nucleotides to an RNA transcript (yielding a sepa- 
rate mRNA) , and a coupled stop-start translation 
of tandem cistrons. 
Influenza virus and paramyxoviruses (SV5) 
were selected for study not only because of their 
importance as the causative agents of major dis- 
eases but also because they provide excellent 
models for examining various properties of inte- 
gral membrane proteins. Since these membrane 
proteins constitute the viruses' major antigenic 
determinants, knowledge about the structure of 
these proteins should enhance our understanding 
of their ability to act as immunological targets, 
thus aiding in developing rationally designed 
therapeutic agents and new means of vaccination. 
We are investigating the mechanism by which 
integral membrane proteins are transported to 
the cell surface in the exocytotic pathway and are 
internalized from the surface by the endocytotic 
pathways. Our model systems include the seven 
integral membrane proteins encoded by influ- 
enza virus and SV5, three of which were discov- 
ered in our laboratory. These prototype mem- 
brane proteins, grouped as types I, II, and III, 
provide a diverse array of viral proteins that span 
the cell membrane once. 
Intracellular Transport of Glycoproteins 
We are determining how polypeptides are ini- 
tially inserted into the endoplasmic reticulum 
and what signals are necessary for the proteins to 
interact with the lipid bilayer. To elucidate the 
rules for protein orientation in the bilayer is a 
prime objective. One of the major factors is the 
presence of positively charged residues flanking 
the hydrophobic membrane-spanning domain to 
retain a region of the protein in the cell cyto- 
plasm. We have also been focusing on the factors 
and signals needed to fold the primary polypep- 
tide chain once it has been translocated across the 
membrane of the endoplasmic reticulum. 
The cellular glucose-regulated protein GRP78- 
BiP is a member of the HSP70 stress family of 
gene products and a resident component of the 
endoplasmic reticulum, where it is thought to 
play a role in the folding and oligomerization 
of secretory and membrane-bound proteins. 
GRP78-BiP also binds to malfolded proteins, and 
this may be one mechanism for preventing their 
intracellular transport. The SV5 hemagglutinin- 
neuraminidase (HN) glycoprotein during its fold- 
ing specifically and transiently associates with 
GRP78-BiP. The fact that this complex formation 
can only be detected before oligomerization of 
the immature HN molecules forms the native tet- 
ramer suggests that GRP78-BiP acts as a chaper- 
one to promote correct folding of the molecule. 
Paramyxovirus infection of cells causes a tran- 
scriptional induction of GRP78-BiP mRNA, and 
our studies indicate that the flux of HN through 
the endoplasmic reticulum, which requires 
GRP78-BiP molecules for its maturation, causes a 
feedback that increases GRP78-BiP transcription. 
To attempt to understand the nature of the spec- 
ificity of GRP78-BiP with a protein, we con- 
structed various altered HN molecules. The data 
indicate that HN contains more than one domain 
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