The inner membrane of mitochondria exhibits a unique three dimensional structure. This membrane is also exceptionally rich in proteins, most of which facilitate transport and catalytic processes. It is assumed that the structure of the inner membrane enables dedicated protein and lipid environments resulting in the spatial organization of protein functions. Accordingly, membrane composition, topology, and function appear to be tightly intertwined. Considering this, it is surprising that we still lack a detailed understanding of how the inner membrane is shaped. Moreover, information on the actual distribution of protein functions in the inner membrane is very scarce at the best. To this end, experimental approaches that provide temporal and spatial information of inner membrane shape and protein localisations are essential to assess and eventually understand how membrane architecture and functional organization are brought about. In this research initiative, we take a decisive step to tackle fundamental questions on mitochondrial ultrastructure and bring together researchers with unique and complementary expertise in mitochondrial imaging technologies with scientists addressing central biological questions on mitochondrial functions.
Investigation of the spatial distribution of OXPHOS complex assembly in mammalian cells
The production of ATP by the oxidative phosphorylation system (OXPHOS) is a vital task of mitochondria. The OXPHOS complexes in the inner membrane assemble from imported and mitochondrial-encoded subunits. This process is thought to progress through transient assembly intermediates that are build and joined in a modular manner. While all imported subunits integrate into the inner membrane at the inner boundary membrane, the topology of assembly processes remains unknown. Here, we aim to dissect the spatial organization and topological heterogeneity of OXPHOS assembly in mammalian cells with a focus on complexes III and IV. We will analyze the composition of assembly intermediates, address mechanisms of the assembly process, and define the spatial organization of assembly steps in the inner mitochondrial membrane. We will analyze, if spatial heterogeneity of assembly processes contributes to the specificity of multi-complex assembly factors and develop new imaging strategies that will allow us to analyze and define the spatial distribution of mitochondrial translation processes.