Inter-alpha-trypsin inhibitor heavy chain 3 as Biomarker for Neuromuscular Disorders: Validation, Specificity and Mechanistic Interactome

• Applicant: Dr. Christina Barbara Menskes
• Subject Area: Molecular and Cellular Neurology and Neuropathology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 539363086

The inter-alpha-trypsin inhibitor heavy chain 3 (ITIH3) is a serine protease inhibitor and contains several complement-binding domains that inhibit the early phase of complement activation and thus mitigate complement-induced organ injury. Myasthenia gravis (MG) is a chronic antibody (Ab)-mediated autoimmune disease disrupting neuromuscular synaptic transmission. Complement activation at the neuromuscular junction is an essential pathophysiological event of MG that has recently become accessible to specific treatment strategies. In a precedent study, we performed in-depth mass spectrometry-based proteomic serum profiling of 114 anti-acetylcholine receptor (AChR)-Ab-positive MG patients. Analysis of the serum proteome combined with machine learning (ML) identified ITIH3 as a serum biomarker reflective of disease activity. The current proposal addresses the validation (work package (WP) I), the specificity (WP II), and the mechanistic interactome of ITIH3 (WP III) by means of mass spectrometry-based proteomics, and ML-based analysis pipelines. For validation purposes of the previous proteomic study, we will assess ITIH3 levels in an independent cohort including a longitudinal follow-up after 12 months (WP I). Beyond MG, we will investigate the disease-specificity of ITIH3 expression in neuromuscular diseases (WP II). For this purpose, we will perform proteomics in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) as a presynaptic autoimmune disorder as opposed to idiopathic inflammatory myopathy (IIM) as a prototypical postsynaptic autoimmune disease. We will map uniquely expressed as well as overlapping protein profiles to further dissect the molecular characteristics of each disease (MG, CIDP, IIM) beyond ITIH3 abundance. For a better mechanistic understanding, we will assess the up- and downstream interactome of ITIH3 using the BioPlex pipeline provided by the Gygi lab (WP III). The protein-protein interactome might reveal therapeutically accessible targets in active autoimmune disease of the neuromuscular axis. In summary, we propose ITIH3 as a biomarker in MG providing information on disease activity that may facilitate therapy decision-making and evaluation. Beyond MG, diagnostic value of ITIH3 is explored in two prototypic neurological diseases, namely CIDP and IIM. For this undertaking, the Gygi lab provides a unique combination of high-end mass spectrometry-based proteomics with outstanding analysis software and pipelines. They have unique expertise in the field of protein interaction studies, proteome-based biomarker discovery and validation. The Walter Benjamin Program would give me the opportunity to further enhance my expertise in proteomic methods and would represent an important career step towards habilitation and the establishment of my own junior research group after my return to Düsseldorf.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professor Dr. Steven P. Gygi