Dataset Information

?-Arrestin-1 mediates thyrotropin-enhanced osteoblast differentiation.

ABSTRACT: Thyrotropin (TSH) activation of the TSH receptor (TSHR), a 7-transmembrane-spanning receptor (7TMR), may have osteoprotective properties by direct effects on bone. TSHR activation by TSH phosphorylates protein kinases AKT1, p38?, and ERK1/2 in some cells. We found TSH-induced phosphorylation of these kinases in 2 cell lines engineered to express TSHRs, human embryonic kidney HEK-TSHR cells and human osteoblastic U2OS-TSHR cells. In U2OS-TSHR cells, TSH up-regulated pAKT1 (7.1±0.5-fold), p38? (2.9±0.4-fold), and pERK1/2 (3.1±0.2-fold), whereas small molecule TSHR agonist C2 had no or little effect on pAKT1 (1.8±0.08-fold), p38? (1.2±0.09-fold), and pERK1/2 (1.6±0.19-fold). Furthermore, TSH increased expression of osteoblast marker genes ALPL (8.2±4.6-fold), RANKL (21±5.9-fold), and osteopontin (OPN; 17±5.3-fold), whereas C2 had little effect (ALPL, 1.7±0.5-fold; RANKL, 1.3±0.6-fold; and OPN, 2.2±0.7-fold). ?-Arrestin-1 and -2 can mediate activatory signals by 7TMRs. TSH stimulated translocation of ?-arrestin-1 and -2 to TSHR, whereas C2 failed to translocate either ?-arrestin. Down-regulation of ?-arrestin-1 by siRNA inhibited TSH-stimulated phosphorylation of ERK1/2, p38?, and AKT1, whereas down-regulation of ?-arrestin-2 increased phosphorylation of AKT1 in both cell types and of ERK1/2 in HEK-TSHR cells. Knockdown of ?-arrestin-1 inhibited TSH-stimulated up-regulation of mRNAs for OPN by 87 ± 1.7% and RANKL by 73 ± 2.4%, and OPN secretion by 74 ± 10%. We conclude that TSH enhances osteoblast differentiation in U2OS cells that is, in part, caused by activatory signals mediated by ?-arrestin-1.

SUBMITTER: Boutin A

PROVIDER: S-EPMC4101659 | biostudies-literature | 2014 Aug

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

β-Arrestin-1 mediates thyrotropin-enhanced osteoblast differentiation.

Boutin Alisa A Eliseeva Elena E Gershengorn Marvin C MC Neumann Susanne S

FASEB journal : official publication of the Federation of American Societies for Experimental Biology 20140410 8

Thyrotropin (TSH) activation of the TSH receptor (TSHR), a 7-transmembrane-spanning receptor (7TMR), may have osteoprotective properties by direct effects on bone. TSHR activation by TSH phosphorylates protein kinases AKT1, p38α, and ERK1/2 in some cells. We found TSH-induced phosphorylation of these kinases in 2 cell lines engineered to express TSHRs, human embryonic kidney HEK-TSHR cells and human osteoblastic U2OS-TSHR cells. In U2OS-TSHR cells, TSH up-regulated pAKT1 (7.1±0.5-fold), p38α (2. ...[more]

PMID: 24723693

Similar Datasets

Project description:Insulin-like growth factor binding protein 2 (IGFBP-2) is important for acquisition of normal bone mass in mice; however, the mechanism by which IGFBP-2 functions is not defined. These studies investigated the role of IGFBP-2 in stimulating osteoblast differentiation. MC-3T3 preosteoblasts expressed IGFBP-2, and IGFBP-2 knockdown resulted in a substantial delay in osteoblast differentiation, reduced osteocalcin expression and Alizarin red staining. These findings were replicated in primary calvarial osteoblasts obtained from IGFBP-2(-/-) mice, and addition of IGFBP-2 rescued the differentiation program. In contrast, overexpression of IGFBP-2 accelerated the time course of differentiation as well as increasing the total number of differentiating cells. By day 6, IGFBP-2-overexpressing cells expressed twice as much osteocalcin as control cultures and this difference persisted. To determine the mechanism by which IGFBP-2 functions, the interaction between IGFBP-2 and receptor tyrosine phosphatase ? (RPTP?) was examined. Disruption of this interaction inhibited the ability of IGFBP-2 to stimulate AKT activation and osteoblast differentiation. Knockdown of RPTP? enhanced osteoblast differentiation, whereas overexpression of RPTP? was inhibitory. Adding back IGFBP-2 to RPTP?-overexpressing cells was able to rescue cell differentiation via enhancement of AKT activation. To determine the region of IGFBP-2 that mediated this effect, an IGFBP-2 mutant that contained substitutions of key amino acids in the heparin-binding domain-1 (HBD-1) was prepared. This mutant had a major reduction in its ability to stimulate differentiation of calvarial osteoblasts from IGFBP-2(-/-) mice. Addition of a synthetic peptide that contained the HBD-1 sequence to calvarial osteoblasts from IGFBP-2(-/-) mice rescued differentiation and osteocalcin expression. In summary, the results clearly demonstrate that IGFBP-2 stimulates osteoblast differentiation and that this effect is mediated through its heparin-binding domain-1 interacting with RPTP?. The results suggest that stimulation of differentiation is an important mechanism by which IGFBP-2 regulates the acquisition of normal bone mass in mice.

Dataset Information

?-Arrestin-1 mediates thyrotropin-enhanced osteoblast differentiation.

Publications

β-Arrestin-1 mediates thyrotropin-enhanced osteoblast differentiation.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets