The Journal of Neuroscience, January 1, 1999, 19(1):64-71
Mechanisms and Structural Determinants of HIV-1 Coat Protein,
gp41-Induced Neurotoxicity
D. Cory
Adamson1, 2,
Kathy L.
Kopnisky1,
Ted M.
Dawson1, 2, and
Valina L.
Dawson1, 2, 3
Departments of 1 Neurology, 2 Neuroscience,
and 3 Physiology, Johns Hopkins University School of
Medicine, Baltimore, Maryland 21287
Of the individuals with human immunodeficiency virus type 1 (HIV-1)
infection, 20-30% will develop the neurological complication of
HIV-associated dementia (HAD). The mechanisms underlying HAD are
unknown; however, indirect immunologically mediated mechanisms are
theorized to play a role. Recently, the HIV-1 coat protein gp41 has
been implicated as a major mediator of HAD through induction of
neurocytokines and subsequent neuronal cell death. Using primary mixed
cortical cultures from neuronal nitric oxide synthase (NOS) null
(nNOS
/
) mice and immunological NOS null
(iNOS
/
) mice, we establish iNOS-derived NO as a
major mediator of gp41 neurotoxicity. Neurotoxicity elicited by gp41 is
markedly attenuated in iNOS
/
cultures compared
with wild-type and nNOS
/
cultures. The NOS
inhibitor L-nitroarginine methyl ester is neuroprotective in wild-type and nNOS
/
cultures, confirming the
role of iNOS-derived NO in gp41 neurotoxicity. Confirming that
iNOS
/
cultures lack iNOS, gp41 did not induce
iNOS in iNOS
/
cultures, but it markedly induced
iNOS in wild-type and nNOS
/
cultures. We
elucidate the region of gp41 that is critical for iNOS induction and
neuronal cell death by monitoring iNOS induction with overlapping
peptides spanning gp41. We show that the N-terminal region of gp41,
which we designate as the neurotoxic domain, induces iNOS protein
activity and iNOS-dependent neurotoxicity at picomolar concentrations
in a manner similar to recombinant gp41 protein. Our experiments
suggest that gp41 is eliciting the induction of iNOS through potential
cell surface receptors or binding sites because the induction of iNOS
is dose dependent and saturable and occurs at physiologically relevant
concentrations. These data confirm that the induction of iNOS by gp41
and the production of NO are primary mediators of neuronal damage and
identify a neurotoxic domain of gp41 that may play an important role in HAD.
Key words:
HIV-1; HIV-associated dementia; neurotoxicity; gp41; immunological nitric oxide synthase; nitric oxide
Copyright © 1999 Society for Neuroscience 0270-6474/99/19164-08$05.00/0