Schnurri-3 regulates ERK downstream of WNT signaling in osteoblasts
Jae-Hyuck Shim, Matthew B. Greenblatt, Weiguo Zou, Zhiwei Huang, Marc N. Wein, Nicholas Brady, Dorothy Hu, Jean Charron, Heather R. Brodkin, Gregory A. Petsko, Dennis Zaller, Bo Zhai, Steven Gygi, Laurie H. Glimcher, Dallas C. Jones
Jae-Hyuck Shim, Matthew B. Greenblatt, Weiguo Zou, Zhiwei Huang, Marc N. Wein, Nicholas Brady, Dorothy Hu, Jean Charron, Heather R. Brodkin, Gregory A. Petsko, Dennis Zaller, Bo Zhai, Steven Gygi, Laurie H. Glimcher, Dallas C. Jones
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Research Article Bone biology

Schnurri-3 regulates ERK downstream of WNT signaling in osteoblasts

Abstract

Mice deficient in Schnurri-3 (SHN3; also known as HIVEP3) display increased bone formation, but harnessing this observation for therapeutic benefit requires an improved understanding of how SHN3 functions in osteoblasts. Here we identified SHN3 as a dampener of ERK activity that functions in part downstream of WNT signaling in osteoblasts. A D-domain motif within SHN3 mediated the interaction with and inhibition of ERK activity and osteoblast differentiation, and knockin of a mutation in Shn3 that abolishes this interaction resulted in aberrant ERK activation and consequent osteoblast hyperactivity in vivo. Additionally, in vivo genetic interaction studies demonstrated that crossing to Lrp5–/– mice partially rescued the osteosclerotic phenotype of Shn3–/– mice; mechanistically, this corresponded to the ability of SHN3 to inhibit ERK-mediated suppression of GSK3β. Inducible knockdown of Shn3 in adult mice resulted in a high–bone mass phenotype, providing evidence that transient blockade of these pathways in adults holds promise as a therapy for osteoporosis.

Authors

Jae-Hyuck Shim, Matthew B. Greenblatt, Weiguo Zou, Zhiwei Huang, Marc N. Wein, Nicholas Brady, Dorothy Hu, Jean Charron, Heather R. Brodkin, Gregory A. Petsko, Dennis Zaller, Bo Zhai, Steven Gygi, Laurie H. Glimcher, Dallas C. Jones

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Figure 1

Screening for functional motifs in SHN3.

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Screening for functional motifs in SHN3. All aa numbering is relative to...
All aa numbering is relative to the reference sequence NP_001121186.1. (A) Truncated SHN3 mutants (1–2,283 aa). WT, 1–1,186 aa; ΔBAS, Δ844–928 aa in 1–1,186 aa; ΔZs1/2 (ZAS1 and ZAS2 deletion), 327–1,719 aa; ΔZs1/2/BAS (ZAS1, ZAS2, and BAS deletion), Δ844–928 in 327–1,719 aa. (B, D, and F) hMSCs were infected with control lentivirus or lentiviruses encoding the indicated SHN3 constructs and cultured in differentiation medium for 21 days. Mineralization activity was analyzed by alizarin red staining. ΔD, D-domain deletion. (C) The aa sequence of the critical region of the BAS domain (p.810–933 aa), containing the D-domain (p.902–910 aa). (E and G) RNA levels of Osx, Bsp, and Ocn, analyzed by RT-PCR, in hMSCs infected by lentiviruses expressing the indicated SHN3 constructs or a control. Values in G are normalized to Hprt. Results are presented as mean + SD.