Identification of HN252 as a potent inhibitor of protein phosphatase PPM1B

Abstract

Protein phosphatase 1B (PPM1B), a member of metal‐dependent protein serine/threonine phosphatase family, is involved in the regulation of several signalling pathways. However, our understanding of its substrate interaction and physiological functions is still largely limited. There is no reported PPM1B inhibitor to date. In this study, we identified HN252, a p‐terphenyl derivative, as a potent PPM1B inhibitor (Ki = 0.52 ± 0.06 µM). HN252 binding to PPM1B displayed remarkable and specific inhibition of PPM1B in both in vitro and ex vivo. With the aid of this small molecular inhibitor, we identified 30 proteins’ serine/threonine phosphorylation as potential substrates of PPM1B, 5 of which were demonstrated by immunoprecipitation, including one known (CDK2) and 4 novel ones (AKT1, HSP90B, β‐catenin and BRCA1). Furthermore, GO and KEGG analysis of dramatically phosphorylated proteins by PPM1B inhibition indicated that PPM1B plays roles in the regulation of multiple cellular processes and signalling pathways, such as gene transcription, inflammatory regulation, ageing and tumorigenesis. Our work provides novel insights into further investigation of molecular mechanisms of PPM1B.

Hematopoietic stem cell fate under the influence of Ser/Thr protein phosphatases

“…For instance, the selective PPM1D inhibitor GSK2830371 suppressed the growth of p53-positive cancer cells in vitro and in animal models(5)(6)(7). In the present study, Lu and colleagues used a new PPM1B inhibitor (HN252), proved its efficiency in animal models, and elegantly validated its specificity in the Ppm1b CKO animals(1,2). This tool will be invaluable for exploring the functions of PPM1B in several systems.…”

“… 5 -7 In the present study, Lu and colleagues used a new PPM1B inhibitor (HN252), proved its efficiency in animal models, and elegantly validated its specificity in the Ppm1b CKO animals. 1 , 2 This tool will be invaluable for exploring the functions of PPM1B in several systems. Additionally, considering the B-cell leukocytopenia observed in Ppm1b CKO mice, it might be interesting to investigate the potential of PPM1B inhibitor in suppressing B-cell leukemias.…”

Phosphatase, Mg²⁺/Mn²⁺ dependent 1B regulates the hematopoietic stem cells homeostasis via the Wnt/β-catenin signaling

“…To explore the role of Ppm1b in HSC function, we first treated the HSC isolated from mouse BM with Ppm1b inhibitor HN252 which we developed in our previous study. 23 The cells in the LSK fraction exhibited a dose-dependent decrease after 48 hours (hr) of culture with HN252, accompanied by the reduced LSK cells ( Figure 1A , Online Supplementary Figure S1B ). HN252 treatment also led to a significant increase in apoptotic cells in the LSK fraction ( Online Supplementary Figure S1C ), but the overall apoptosis rate was relatively low (<5%), suggesting that cell death is not the main cause of impaired HSC expansion induced by HN252.…”

“… 22 Our previous study suggested that Ppm1b may participate in the regulation of hematopoietic processes such as B-/T-cell receptor signaling, FOXO signaling, and the pathogenesis of leukemia. 23 It had consistently been reported that Ppm1b regulates terminal erythropoiesis by interacting with an erythroid Kruppel-like factor. 24 However, the role of Ppm1b in hematopoiesis is still largely unknown.…”