Proteomics of Protein Trafficking

Abstract

Organs are interdependent and specialized – they communicate to enable organismal processes including growth, energy metabolism, and reproduction. Secreted peptides and proteins are essential regulators of homeostasis, and they compose a poorly-characterized communication network. Secreted factors are also relevant for disease: obesity affects 40% of the US population and results from poorly-characterized dysfunctional systemic signaling. Despite their relevance to homeostasis and disease, many additional factors remain to be identified. Characterizing the factors involved has been challenging, because conventional methods cannot identify low-abundance proteins or their origins and destinations. The broad goal of my new laboratory at Scripps is to apply novel high-throughput quantitative approaches we developed to interorgan communication in mammals, in order to understand the identity of the factors involved, which organs they originate from and target, their functions, and regulation of their production in disease. In this ASBMB Annual Meeting talk, I will describe our recent work and progress in establishing a proteomic platform, in which we biotinylate all proteins in a subcellular compartment of one organ using the engineered promiscuous biotin ligase BirA*G3 (a relative of TurboID), and then affinity-enrich the biotinylated proteins, identify them from distant organs using quantitative proteomics. This platform therefore allows simplifying the proteome and identifying low-abundance proteins, as well as their organs of origin and destination. Using this system in Drosophila, we identified 269 fat body secreted proteins in muscles, which included growth factors, cytokines, and proteins with receptors in muscles. In particular, I will present the characterization of muscle phenotypes of a fat body-derived protein CG2145. In addition to these data, I will describe our ongoing work on transitioning this method to mammalian systems. Altogether, this approach should be widely applicable to studies of secretome trafficking networks in vivo, including non-conventional secretion, in both arthropod and mammalian systems, in healthy or diseased states.