title: Organelle biogenesis and interorganellar connections: Better in contact than in isolation.
abstract: Membrane contact sites (MCSs) allow the exchange of molecules and information between organelles, even when their membranes cannot fuse directly. In recent years, a number of functions have been attributed to these contacts, highlighting their critical role in cell homeostasis. Although inter-organellar connections typically involve the endoplasmic reticulum (ER), we recently reported the presence of a novel MCSs between melanosomes and mitochondria. Melanosome-mitochondrion contacts appear mediated by fibrillar bridges resembling the protein tethers linking mitochondria and the ER, both for their ultrastructural features and the involvement of Mitofusin 2. The frequency of these connections correlates spatially and timely with melanosome biogenesis, suggesting a functional link between the 2 processes and in general that organelle biogenesis in the secretory pathway requires interorganellar crosstalks at multiple steps. Here, we summarize the different functions attributed to MCSs, and discuss their possible relevance for the newly identified melanosome-mitochondrion liaison.
authors.affiliation: San Raffaele Scientific Institute; Experimental Imaging Center; Milan, Italy ; University of Genoa; Department of Experimental Medicine; Genoa, Italy.
authors.forename: Tiziana
authors.initials: T
authors.lastname: Daniele
authors.affiliation: San Raffaele Scientific Institute; Division of Genetics and Cell Biology; Milan, Italy.
authors.forename: Maria Vittoria
authors.initials: MV
authors.lastname: Schiaffino
keywords: ATP supply; calcium signaling; cytosolic microdomains; lipid transfer; lysosome-related organelles; organelle dynamics; protein-protein interactions