Publications

Abstract

Autosomal dominant hyper IgE syndrome (AD-HIES) is a primary immunodeficiency caused by heterozygous dominant negative mutations in the gene encoding Signal transducer and activator of transcription 3 (STAT3). These mutations cause a multi systemic disorder characterized immunologically by susceptibility to infection with pathogens such as C. albicans and S. aureus due to defective Th17 responses, and a failure to generate effective humoral immune responses. Interestingly, disease-causing mutations have been identified throughout all functional domains of STAT3 including the DNA binding, SH2 and transactivation domains. However, no phenotype-genotype correlations have been observed. To better understand how different mutations all result in the same clinical and functional outcome we sought to characterize which stage(s) of STAT3 signaling was impaired by each of these mutations and if this was consistent for mutations in different domains. We used Bcelllines from AD-HIES patients or cell lines transfected with mutant STAT3 to determine the abilities of mutant STAT3 proteins to undergo phosphorylation, cytokine receptor docking, dimerization, nuclear translocation, bind DNA and induce gene transcription. Our analysis revealed that while all mutations resulted in a distal impairment in STAT3 binding to DNA, the block occurred at different proximal stages in signaling: transactivation domain mutant had reduced phosphorylation, SH2 domain mutants either were not phosphorylated or had reduced dimerization, and DNA binding domain mutants had defective nuclear translocation or DNA binding. Thus, this study reveals the biochemical mechanisms underlying dysfunctional STAT3 signaling in AD-HIES and also identifies residues and regions of domains that are critical for normal STAT3 function.