Signaling by covalent heterodimers of interferon-gamma. Evidence for one-sided signaling in the active tetrameric receptor complex.
Interferon-gamma (IFN-gamma) and its receptor complex are dimeric and bilaterally symmetric. We created mutants of IFN-gamma that bind only one IFN-gammaR1 chain per dimer molecule (called a monovalent IFN-gamma) to see if the interaction of IFN-gamma with one-half of the receptor complex is sufficient for bioactivity. Mutating a receptor-binding sequence in either AB loop of a covalent dimer of IFN-gamma yielded two monovalent IFN-gammas, gamma(m)-gamma and gamma-gamma(m), which cross-link to only a single soluble IFN-gammaR1 molecule in solution and on the cell surface. Monovalent IFN-gamma competes fully with wild type IFN-gamma for binding to U937 cells but only at a greater than 100-fold higher concentration than wild type IFN-gamma. Monovalent IFN-gamma had anti-vesicular stomatitis virus activity and antiproliferative activity, and it induced major histocompatibility complex class I and class II (HLA-DR) expression. In contrast, the maximal levels of activated Stat1alpha produced by monovalent IFN-gammas after 15 min were never more than half of those produced by either wild type or covalent IFN-gammas in human cell lines. These data indicate that while monovalent IFN-gamma activates only one-half of a four-chain receptor complex, this is sufficient for Stat1alpha activation, major histocompatibility complex class I surface antigen induction, and antiviral and antiproliferative activities. Thus, while interaction with both halves of the receptor complex is required for high affinity binding of IFN-gamma and efficient signal transduction, interaction with only one-half of the receptor complex is sufficient to initiate signal transduction.
Krause
C D
CD
Department of Molecular Genetics and Microbiology, The Graduate School of Biomedical Sciences, The University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
Lunn
C A
CA
Izotova
L S
LS
Mirochnitchenko
O
O
Kotenko
S V
SV
Lundell
D J
DJ
Narula
S K
SK
Pestka
S
S
D001483:Base Sequence; D001704:Biopolymers; D002460:Cell Line; D002850:Chromatography, Gel; D017931:DNA Primers; D019281:Dimerization; D006801:Humans; D007371:Interferon-gamma / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017471:Receptors, Interferon / Q000378:metabolism*; D015398:Signal Transduction; D000096743:Interferon gamma Receptor
D001704:Biopolymers; D017931:DNA Primers; D007371:Interferon-gamma; D017471:Receptors, Interferon; D000096743:Interferon gamma Receptor