Inhibition of PPP1R15A alleviates osteoporosis via suppressing RANKL-induced osteoclastogenesis

Zong-bao Ding1,2, Yan Chen1, Yu-rong Zheng3, Yi-yuan Wang1, Wen-de Deng1, Jie-huang Zheng1, Qin Yang1, Zi-ye Chen1, Li-hong Li1, Hui Jiang3, Xiao-juan Li1
1 Laboratory of Anti-inflammatory and Immunomodulatory Pharmacology, Innovation Program of Drug Research on Inflammatory and Immune Diseases, NMPA Key Laboratory for Research and Evaluation of Drug Metabolism & Guangdong Provincial Key Laboratory of New Drug Screening, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou 510515, China
2 Department of Bioengineering, Zhuhai Campus of Zunyi Medical University, Zhuhai 519041, China
3 Division of Spine Surgery, Department of Orthopedics, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China
Correspondence to: Hui Jiang:, Xiao-juan Li:,
DOI: 10.1038/s41401-023-01209-0
Received: 25 April 2023
Accepted: 28 November 2023
Advance online: 8 January 2024


Osteoporosis results from overactivation of osteoclasts. There are currently few drug options for treatment of this disease. Since the successful development of allosteric inhibitors, phosphatases have become attractive therapeutic targets. Protein phosphatase 1, regulatory subunit 15 A (PPP1R15A), is a stress-responsive protein, which promotes the UPR (unfolded protein response) and restores protein homeostasis. In this study we investigated the role of PPP1R15A in osteoporosis and osteoclastogenesis. Ovariectomy (OVX)-induced osteoporosis mouse model was established, osteoporosis was evaluated in the left femurs using micro-CT. RANKL-stimulated osteoclastogenesis was used as in vitro models. We showed that PPP1R15A expression was markedly increased in BMMs derived from OVX mice and during RANKL-induced osteoclastogenesis in vitro. Knockdown of PPP1R15A or application of Sephin1 (a PPP1R15A allosteric inhibitor in a phase II clinical trial) significantly inhibited osteoclastogenesis in vitro. Sephin1 (0.78, 3.125 and 12.5 μM) dose-dependently mitigated the changes in NF-κB, MAPK, and c-FOS and the subsequent nuclear factor of activated T cells 1 (NFATc1) translocation in RANKL-stimulated BMMs. Both Sephin1 and PPP1R15A knockdown increased the phosphorylated form of eukaryotic initiation factor 2α (eIF2α); knockdown of eIF2α reduced the inhibitory effects of Sephin1 on NFATc1-luc transcription and osteoclast formation. Furthermore, Sephin1 or PPP1R15A knockdown suppressed osteoclastogenesis in CD14+ monocytes from osteoporosis patients. In OVX mice, injection of Sephin1 (4, 8 mg/kg, i.p.) every two days for 6 weeks significantly inhibited bone loss, and restored bone destruction and decreased TRAP-positive cells. This study has identified PPP1R15A as a novel target for osteoclast differentiation, and genetic inhibition or allosteric inhibitors of PPP1R15A, such as Sephin1, can be used to treat osteoporosis.

Keywords: osteoporosis; PPP1R15A; Sephin1; osteoclastogenesis; RANKL; eIF2α

Article Options

Download Citation

Cited times in Scopus