Structure and Replication of Influenza Virus 
and Paramyxoviruses 
Robert A. Lamb, Ph.D., Sc.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. and Sc.D. degrees 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. Ten years ago he joined the faculty of Northwestern University. 
ANIMAL viruses provide a unique tool with 
which to study the complex biochemical 
processes involved in the biosynthesis and main- 
tenance of eukaryotic cells. Our laboratory is in- 
vestigating the molecular structure and the mech- 
anism of replication of two enveloped RNA 
viruses, influenza virus and the paramyxovi- 
rus SV5. 
Influenza virus causes important diseases in 
humans and animals. It has tremendous socioeco- 
nomic consequences, for influenza continues to 
occur in regular epidemics and occasional pan- 
demics and is a leading cause of morbidity and 
mortality. Paramyxoviruses cause many biologi- 
cally and economically important diseases of hu- 
mans and lower animals. Besides SV5, these vi- 
ruses include parainfluenza virus types 1-5, 
mumps virus, measles virus, canine distemper 
virus, Newcastle disease virus of chickens, and 
rinderpest of cattle. 
We have been elucidating the wide range of 
mechanisms used by these RNA viruses to maxi- 
mize the amount of encoded protein in their 
compact genomes. We have identified overlap- 
ping reading frames, splicing of mRNAs, the use 
of bicistronic mRNAs, transcriptional stuttering 
to add nontemplated nucleotides to an RNA tran- 
script (and hence yield a separate mRNA) , and a 
coupled stop-start translation of tandem cistrons. 
Influenza virus and SV5 were selected for study 
not only because of their importance as the caus- 
ative agents of major diseases but also because 
they provide excellent models for examining a 
variety of properties of integral membrane pro- 
teins. Since these proteins are the major antigenic 
determinants of the viruses, knowledge about 
their structure should enhance our understand- 
ing of how they act as immunological targets, 
thus aiding in developing new vaccines. In addi- 
tion, some of the biochemical activities of the 
influenza virus are specialized to the virus, mak- 
ing them attractive as points of intervention in 
the virus life cycle to which rationally designed 
therapeutic agents can be developed. We are ana- 
lyzing biochemical properties of the viral 
glycoproteins. 
We are also investigating the mechanism by 
which integral membrane proteins are trans- 
ported to the cell surface in the exocytotic path- 
ways and are internalized from the surface by the 
endocytotic pathways. We are studying the seven 
integral membrane proteins encoded by influ- 
enza virus and SV5 — three of which were discov- 
ered in our laboratory — because they provide a 
diverse group of membrane proteins that span the 
cell membrane once. 
Virus Cation Channels 
Influenza virus protein M2 is a small (97-resi- 
due) type-Ill integral membrane protein that 
forms a disulfide-linked tetramer. The sensitivity 
of influenza virus to the drug amantadine hydro- 
chloride, the coupling of antiviral action to the 
M2 transmembrane domain, and the premature 
acid-induced conformational change in the viral 
hemagglutinin in the presence of the drug sug- 
gest that M2 is an ion channel, that it is essential 
for virus uncoating in secondary endosomes, and 
that it can alter the intracellular pH of the trans 
Golgi network. In collaboration with Lawrence 
Pinto, Northwestern University, we have tested 
the M2 protein for ion channel activity by inject- 
ing M2 mRNA into Xenopus oocytes and measur- 
ing surface currents with a two-electrode patch- 
clamp apparatus. We have shown that expression 
of the protein is associated with an ion channel 
activity selective for monovalent ions. 
Amantadine hydrochloride significantly atten- 
uated the inward current induced by hyperpolar- 
ization of oocyte membranes, and mutations in 
the M2 membrane-spanning domain that confer 
viral resistance to amantadine produced currents 
that were resistant to the drug. Thus we have pro- 
vided direct data on the antiviral drug's mecha- 
nism of action. 
The M2 protein does not have the molecular 
structure of most ion channels cloned to date. We 
had to perform a large number of experiments to 
eliminate the possibility that the M2 protein was 
not a regulator that activates a normally silent 
channel endogenous to oocytes. Our analysis of 
distinguishing characteristics of the currents pro- 
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