Magnesium-sensitive upstream ORF controls PRL phosphatase expression to mediate energy metabolism

Phosphatases of regenerating liver (PRL-1, PRL-2, and PRL-3, also known as PTP4A1, PTP4A2, and PTP4A3) control magnesium homeostasis through an association with the CNNM magnesium transport regulators. Although high PRL levels have been linked to cancer progression, regulation of their expression is poorly understood. Here we show that modulating intracellular magnesium levels correlates with a rapid change of PRL expression by a mechanism involving its 5'UTR mRNA region. Mutations or CRISPR-Cas9 targeting of the conserved upstream ORF present in the mRNA leader derepress PRL protein synthesis and attenuate the translational response to magnesium levels. Mechanistically, magnesium depletion reduces intracellular ATP but up-regulates PRL protein expression via activation of the AMPK/mTORC2 pathway, which controls cellular energy status. Hence, altered PRL-2 expression leads to metabolic reprogramming of the cells. These findings uncover a magnesium-sensitive mechanism controlling PRL expression, which plays a role in cellular bioenergetics.

Phosphatase of regenerating liver in hematopoietic stem cells and hematological malignancies

The phosphatases of regenerating liver (PRLs), consisting PRL1, PRL2 and PRL3, are dual-specificity protein phosphatases that have been implicated as biomarkers and therapeutic targets in several solid tumors. However, their roles in hematological malignancies are largely unknown. Recent findings demonstrate that PRL2 is important for hematopoietic stem cell self-renewal and proliferation. In addition, both PRL2 and PRL3 are highly expressed in some hematological malignancies, including acute myeloid leukemia (AML), chronic myeloid leukemia (CML), multiple myeloma (MM) and acute lymphoblastic leukemia (ALL). Moreover, PRL deficiency impairs the proliferation and survival of leukemia cells through regulating oncogenic signaling pathways. While PRLs are potential novel therapeutic targets in hematological malignancies, their exact biological function and cellular substrates remain unclear. This review will discuss how PRLs regulate hematopoietic stem cell behavior, what signaling pathways are regulated by PRLs, and how to target PRLs in hematological malignancies. An improved understanding of how PRLs function and how they are regulated may facilitate the development of PRL inhibitors that are effective in cancer treatment.

MiR-29c mediates epithelial-to-mesenchymal transition in human colorectal carcinoma metastasis via PTP4A and GNA13 regulation of β-catenin signaling

BACKGROUND

Distant metastasis is the major cause of cancer-related death, and epithelial-to-mesenchymal transition (EMT) has a critical role in this process. Accumulating evidence indicates that EMT can be regulated by microRNAs (miRNAs). miR-29c has been implicated as a tumor suppressor in several human cancers. However, the role of miR-29c in the progression of colorectal cancer (CRC) metastasis remains largely unknown.

PATIENTS AND METHODS

The expression of miR-29c was examined by qRT-PCR in a cohort of primary CRC (PC) and distant liver metastasis (LM) tissues. A series of in vivo and in vitro assays were carried out in order to elucidate the functions of miR-29c and the molecular mechanisms underlying the pathogenesis of metastatic CRC.

RESULTS

miR-29c was markedly downregulated in PCs with distant metastasis and determined to be an independent predictor of shortened patient survival. But LM tissues showed higher levels of miR-29c than that in PC tissues. In CRC cells, miR-29c dramatically suppressed cell migration and invasion abilities in vitro and cancer metastasis in vivo. In addition, miR-29c inhibited EMT and negatively regulated Wnt/β-catenin signaling pathway. Guanine nucleotide binding protein alpha13 (GNA13) and protein tyrosine phosphatase type IVA (PTP4A) were identified as direct targets of miR-29c, which acted through ERK/GSK3β/β-catenin and AKT/GSK3β/β-catenin pathways, respectively, to regulate EMT. Furthermore, significant associations between miR-29c, its target genes (GNA13 and PTP4A) and EMT markers were validated in both PC and LM tissues.

CONCLUSION

Our findings highlight the important role of miR-29c in regulating CRC EMT via GSK-3β/β-catenin signaling by targeting GNA13 and PTP4A and provide new insights into the metastatic basis of CRC.