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- Title
APPL1, an Adiponectin Receptor Binding Partner, Is Phosphorylated at Ser<sup>401</sup> in Human Skeletal Muscle In Vivo.
- Authors
Mapes, Rebekka; Zhengping Yi; Langlais, Paul; Riojas, Ramon; Feng Liu; Dong, Lily Q.; Mandarino, Lawrence J.
- Abstract
Adiponectin has gained much attention recently due to its insulin sensitizing effects on lipid and glucose metabolism. Serum concentrations of adiponectin are low in insulin resistance, and expression of adiponectin receptors (adipoR) is reduced in insulin resistant human skeletal muscle. The adiponectin signaling pathway is mainly unknown, but recently an adaptor protein termed APPL 1 (a̱daptor protein containing p̱leckstrin homology domain, p̱hosphotyrosine binding domain and ḻeucine zipper motif has been shown to interact directly with adipoR1. APPL1 is present in C2C12 myoblasts and mouse skeletal muscle; however, no studies have identified APPL1 in humans. To determine the abundance of APPL1 protein in human skeletal muscle, immunoprecipitation and western blot analysis indicated a band specific to APPL1. In addition to western blot analysis, immunoprecipitated APPL1 was subjected to tryptic digestion and HPLC-nanospray-MS/MS analysis, which unambiguously identified APPL1, with 36% sequence coverage, thus confirming its presence in human skeletal muscle. Finally, targeted phosphopeptide analysis using HPLC-nanospray-MS/MS indicated APPL1 was phosphorylated specifically on Set[sup 401]. Aphosphospecific antibody produced against Set[sup 401] specifically recognized APPL1 phosphorylation in human skeletal muscle. In summary, APPL1 is abundantly expressed in human skeletal muscle and is phosphorylated in vivo on Ser[sup 401]. ADA-Funded Research
- Subjects
CARRIER proteins; MUSCLE proteins; PHOSPHORYLATION; MUSCULOSKELETAL system; INSULIN resistance
- Publication
Diabetes, 2007, Vol 56, pA508
- ISSN
0012-1797
- Publication type
Article