title: In vivo phosphoproteome of human skeletal muscle revealed by phosphopeptide enrichment and HPLC-ESI-MS/MS.
abstract: Protein phosphorylation plays an essential role in signal transduction pathways that regulate substrate and energy metabolism, contractile function, and muscle mass in human skeletal muscle. Abnormal phosphorylation of signaling enzymes has been identified in insulin-resistant muscle using phosphoepitope-specific antibodies, but its role in other skeletal muscle disorders remains largely unknown. This may be in part due to insufficient knowledge of relevant targets. Here, we therefore present the first large-scale in vivo phosphoproteomic study of human skeletal muscle from 3 lean, healthy volunteers. Trypsin digestion of 3-5 mg human skeletal muscle protein was followed by phosphopeptide enrichment using SCX and TiO(2). The resulting phosphopeptides were analyzed by HPLC-ESI-MS/MS. Using this unbiased approach, we identified 306 distinct in vivo phosphorylation sites in 127 proteins, including 240 phosphoserines, 53 phosphothreonines, and 13 phosphotyrosines in at least 2 out of 3 subjects. In addition, 61 ambiguous phosphorylation sites were identified in at least 2 out of 3 subjects. The majority of phosphoproteins detected are involved in sarcomeric function, excitation-contraction coupling (the Ca(2+)-cycle), glycolysis, and glycogen metabolism. Of particular interest, we identified multiple novel phosphorylation sites on several sarcomeric Z-disk proteins known to be involved in signaling and muscle disorders. These results provide numerous new targets for the investigation of human skeletal muscle phosphoproteins in health and disease and demonstrate feasibility of phosphoproteomics research of human skeletal muscle in vivo.
authors.affiliation: Center for Metabolic Biology, Arizona State University, Tempe, Arizona 85287-3704, USA.
authors.forename: Kurt
authors.initials: K
authors.lastname: Højlund
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Bowen
authors.forename: Hyonson
authors.initials: H
authors.lastname: Hwang
authors.forename: Charles R
authors.initials: CR
authors.lastname: Flynn
authors.forename: Lohith
authors.initials: L
authors.lastname: Madireddy
authors.forename: Thangiah
authors.initials: T
authors.lastname: Geetha
authors.forename: Paul
authors.initials: P
authors.lastname: Langlais
authors.forename: Christian
authors.initials: C
authors.lastname: Meyer
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Mandarino
authors.forename: Zhengping
authors.initials: Z
authors.lastname: Yi
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D019295:Computational Biology; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000032:analysis*; D018482:Muscle, Skeletal / Q000737:chemistry*; D010748:Phosphopeptides / Q000737:chemistry*; D010766:Phosphorylation; D020543:Proteome / Q000032:analysis; D040901:Proteomics / Q000379:methods; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D009124:Muscle Proteins; D010748:Phosphopeptides; D020543:Proteome