Correct maturation of collagen molecules is critical for cellular development and physiology, and for tissue organization into functional compartments, including organs, extracellular matrix and connective tissue. In 2016, a novel pathway regulating collagen trafficking was proposed, and its essential components were identified (Figure 1). Central to this pathway are two trafficking proteins VPS33B and VIPAR (core CHEVI complex) which have been identified as primarily responsible for the trafficking of at least one enzyme responsible of collagen post-translational modifications, the lysyl- hydroxylase 3 (LH3). Genetic mutations in both the core CHEVI complex and its cargo enzyme induce rare but highly invalidating and often lethal phenotypes, characterized by abnormal collagen distribution and/or maturation often linked to impairment in endosomal trafficking. Moreover, the cargo enzyme and its human homologues, LH1 and LH2, have been found implicated in the progression of cancer metastatization. Mechanisms of LH secretion in metastatic cancers have not been identified, although we can speculate about an involvement of the CHEVI complex.
In the time of this Marie Curie Individual Fellowship, I characterized the molecular players constituting the CHEVI complex and their cargo (Figure 1). I obtained structural information of the core CHEVI complex produced in mammalian cell lines, by combining small angle X-ray scattering analysis with cross-linking and native mass spectrometry (MS). In parallel, I contributed to the structural and functional characterization of its cargo LH3, combining X-ray crystallography, electron microscopy (EM), mutagenesis scanning and activity assays and expanded the study to the entire LH family. Overall, the discoveries made in the timefame of COTETHERS project represent to date an invaluable resource for the society, since they will have direct impact on treatment of highly invalidating health conditions.
