Single muscle fiber proteomics reveals unexpected mitochondrial specialization

Mammalian skeletal muscles are composed of multinucleated cells termed slow or fast fibers according to their contractile and metabolic properties. Here, we developed a high-sensitivity workflow to characterize the proteome of single fibers. Analysis of segments of the same fiber by traditional and unbiased proteomics methods yielded the same subtype assignment. We discovered novel subtype-specific features, most prominently mitochondrial specialization of fiber types in substrate utilization. The fiber type-resolved proteomes can be applied to a variety of physiological and pathological conditions and illustrate the utility of single cell type analysis for dissecting proteomic heterogeneity. Synopsis Here, single multinucleated muscle fibers are analyzed by high sensitivity proteomics for the first time. This reveals an unexpected diversity and specialization in metabolic properties of individual fiber types, in particular in mitochondrial function. First single skeletal muscle fiber proteome, and thereby single cell proteome of any kind Single-shot proteomic analysis captures main features of type 1-slow and of the subtypes of fast fibers Qualitative differences in the mitochondrial proteome of the four fiber types uncover a metabolic specialization Here, single multinucleated muscle fibers are analyzed by high sensitivity proteomics for the first time. This reveals an unexpected diversity and specialization in metabolic properties of individual fiber types, in particular in mitochondrial function.