Functional analysis of naturally occurring amino acid substitutions in human IFN-γR1

IFN-gamma plays an essential role in the IL-12/IL-23/IFN-gamma pathway that is required for the defense against intracellular pathogens In the IFN-gamma R1 several amino acid substitutions have been reported that abrogate IFN-gamma signaling. These substitutions Can lead to a null phenotype and enhanced Susceptibility to infection by poorly pathogenic mycobacteria, a disorder known as Mendelian Susceptibility to Mycobacterial Disease (MSMD) More common amino acid variations in the IFN-gamma R1 may also influence IFN-gamma R function, albeit more subtle To determine the effect of various amino acid Substitutions on IFN-gamma R1 expression and function we cloned two newly identified amino acid Substitutions (S149L, 1352M), four common variations (V14M, V61I, H335P, L467P). seven reported missense mutations (V61Q, V63G, Y66C, C77Y, C77F, C85Y, I87T) and the 818delTTAA mutation in a retroviral expression vector IFN-gamma R1 expression was determined as well as responsiveness to IFN-gamma stimulation. The two newly discovered variants, and the four common polymorphisms Could be detected oil the cell Surface, however, the V14M, H335P and I352M variants were significantly lower expressed at the cell membrane, compared to the wild type receptor Despite the variance in cell surface expression. these IFN-gamma R1 variants did not affect function In contrast to literature. in our model the expression of the V63G variant was severely reduced and its function was severely impaired but not completely abrogated In addition, we confirmed the severely reduced function of the I87T mutant receptor, the completely abrogated expression and function of the V61E, V61Q, C77F, C77Y and the C85Y mutations. as well as the overexpression pattern of the 818delTTAA mutant receptor The Y66C mutation was expressed at the cell surface, it was however, not functional We conclude that the V14M, V61I, S149L, H335P, I352M and L467P are functional polymorphisms The other variants are deleterious mutations with V61E, V61Q, Y66C, C77F, C77Y and C85Y leading to complete IFN-gamma R1 deficiency, while V63G and 187T lead to partial IFN-gamma R1 deficiency (C) 2009 Elsevier Ltd All rights reserved.