title: T-cell protein tyrosine phosphatase regulates bone resorption and whole-body insulin sensitivity through its expression in osteoblasts.
abstract: Insulin signaling in osteoblasts contributes to whole-body glucose homeostasis in the mouse and in humans by increasing the activity of osteocalcin. The osteoblast insulin signaling cascade is negatively regulated by ESP, a tyrosine phosphatase dephosphorylating the insulin receptor. Esp is one of many tyrosine phosphatases expressed in osteoblasts, and this observation suggests that other protein tyrosine phosphatases (PTPs) may contribute to the attenuation of insulin receptor phosphorylation in this cell type. In this study, we sought to identify an additional PTP(s) that, like ESP, would function in the osteoblast to regulate insulin signaling and thus affect activity of the insulin-sensitizing hormone osteocalcin. For that purpose, we used as criteria expression in osteoblasts, regulation by isoproterenol, and ability to trap the insulin receptor in a substrate-trapping assay. Here we show that the T-cell protein tyrosine phosphatase (TC-PTP) regulates insulin receptor phosphorylation in the osteoblast, thus compromising bone resorption and bioactivity of osteocalcin. Accordingly, osteoblast-specific deletion of TC-PTP promotes insulin sensitivity in an osteocalcin-dependent manner. This study increases the number of genes involved in the bone regulation of glucose homeostasis.
authors.affiliation: Department of Genetics and Development, Columbia University Medical Center, New York, New York, USA.
authors.forename: Tiffany
authors.initials: T
authors.lastname: Zee
authors.forename: Carmine
authors.initials: C
authors.lastname: Settembre
authors.forename: Robert L
authors.initials: RL
authors.lastname: Levine
authors.forename: Gerard
authors.initials: G
authors.lastname: Karsenty
mesh_terms: D000818:Animals; D001862:Bone Resorption; D002478:Cells, Cultured; D017353:Gene Deletion; D015870:Gene Expression; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000378:metabolism*; D015675:Osteocalcin / Q000378:metabolism; D011485:Protein Binding; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1 / Q000235:genetics / Q000378:metabolism; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2 / Q000235:genetics / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism
chemical_list: D007328:Insulin; D015675:Osteocalcin; D011972:Receptor, Insulin; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2; C516609:Ptpn1 protein, mouse