Metal dependent protein phosphatase PPM family in cardiac health and diseases

PPM1G and its diagnostic, prognostic and therapeutic potential in HCC (Review)

Global statistics indicate that hepatocellular carcinoma (HCC) is the sixth most common cancer and the third leading cause of cancer‑related death. Protein phosphatase Mg2+/Mn2+ dependent 1G (PPM1G, also termed PP2Cγ) is one of the 17 members of the PPM family. The enzymatic activity of PPM1G is highly reliant on Mg2+ or Mn2+ and serves as a dephosphorylation regulator for numerous key proteins. PPM1G, functioning as a phosphatase, is involved in a number of significant biological processes such as the regulation of eukaryotic gene expression, DNA damage response, cell cycle and apoptosis, cell migration ability, cell survival and embryonic nervous system development. Additionally, PPM1G serves a role in regulating various signaling pathways. In recent years, further research has increasingly highlighted PPM1G as an oncogene in HCC. A high expression level of PPM1G is closely associated with the occurrence, progression and poor prognosis of HCC, offering notable diagnostic and therapeutic value for this patient population. In the present review, the regulatory role of PPM1G in diverse biological processes and signaling pathway activation in eukaryotes is evaluated. Furthermore, its potential application as a biomarker in the diagnosis and prognosis evaluation of HCC is assessed, and future prospects for HCC treatment strategies centered on PPM1G are discussed.

Maintaining Genome Integrity: Protein Kinases and Phosphatases Orchestrate the Balancing Act of DNA Double-Strand Breaks Repair in Cancer

DNA double-strand breaks (DSBs) are the most lethal DNA damages which lead to severe genome instability. Phosphorylation is one of the most important protein post-translation modifications involved in DSBs repair regulation. Kinases and phosphatases play coordinating roles in DSB repair by phosphorylating and dephosphorylating various proteins. Recent research has shed light on the importance of maintaining a balance between kinase and phosphatase activities in DSB repair. The interplay between kinases and phosphatases plays an important role in regulating DNA-repair processes, and alterations in their activity can lead to genomic instability and disease. Therefore, study on the function of kinases and phosphatases in DSBs repair is essential for understanding their roles in cancer development and therapeutics. In this review, we summarize the current knowledge of kinases and phosphatases in DSBs repair regulation and highlight the advancements in the development of cancer therapies targeting kinases or phosphatases in DSBs repair pathways. In conclusion, understanding the balance of kinase and phosphatase activities in DSBs repair provides opportunities for the development of novel cancer therapeutics.

Structural basis for the specificity of PPM1H phosphatase for Rab GTPases

LRRK2 serine/threonine kinase is associated with inherited Parkinson's disease. LRRK2 phosphorylates a subset of Rab GTPases within their switch 2 motif to control their interactions with effectors. Recent work has shown that the metal-dependent protein phosphatase PPM1H counteracts LRRK2 by dephosphorylating Rabs. PPM1H is highly selective for LRRK2 phosphorylated Rabs, and closely related PPM1J exhibits no activity towards substrates such as Rab8a phosphorylated at Thr72 (pThr72). Here, we have identified the molecular determinant of PPM1H specificity for Rabs. The crystal structure of PPM1H reveals a structurally conserved phosphatase fold that strikingly has evolved a 110-residue flap domain adjacent to the active site. The flap domain distantly resembles tudor domains that interact with histones in the context of epigenetics. Cellular assays, crosslinking and 3-D modelling suggest that the flap domain encodes the docking motif for phosphorylated Rabs. Consistent with this hypothesis, a PPM1J chimaera with the PPM1H flap domain dephosphorylates pThr72 of Rab8a both in vitro and in cellular assays. Therefore, PPM1H has acquired a Rab-specific interaction domain within a conserved phosphatase fold.