Potential suppressive functions of microRNA-504 in cervical cancer cells malignant process were achieved by targeting PAICS and regulating EMT.

PURPOSE: The present study aimed to investigate the effects of miR-504 in cervical cancer. METHODS: Normal and cervical cancer tissue specimens derived from TCGA and GTEx databases were employed to analyze the miR-504 and PAICS (one of potential target gene of miR-504) expression. Kaplan-Meier strategy was applied to analyze the prognostic powers of miR-504 and PAICS. The proliferation, clonogenic ability, invasion, and migration of cervical cancer cells (C-33A and HeLa) were detected using Cell Counting Kit 8, colony formation, and transwell assays. Pearson correlation analysis was used to assess the correlation between miR-504 and PAICS, which was confirmed using luciferase reporter assay. The mRNA and protein levels were detected by qRT-PCR and western blot, respectively. RESULTS: TCGA data revealed that miR-504 expression might be decreased in cervical cancer, which was correlated with unfavorable prognosis. Further experiments exhibited that abnormal miR-504 expression negatively affected malignant cellular behaviors in cervical cancer, including proliferation, colony formation, invasion, and migration. PAICS was identified as a putative target of miR-504, and negatively related with miR-504 expression. PAICS expression was increased in cervical cancer and its high-regulation-induced worse outcomes of patients with cervical cancer. Rescue experiments indicated that PAICS restricted the impacts of miR-504 in cervical cancer cells. Analysis of western blot suggested that overexpression of PAICS overturned the miR-504-induced EMT inactivation. CONCLUSION: Our observations elucidated that miR-504, acting as a suppressor for the progression of cervical cancer, inhibits cell proliferation, invasion and migration, and mediates EMT via negatively regulating PAICS.

Molecular mechanism of ERK dephosphorylation by striatal-enriched protein tyrosine phosphatase.

Striatal-enriched tyrosine phosphatase (STEP) is an important regulator of neuronal synaptic plasticity, and its abnormal level or activity contributes to cognitive disorders. One crucial downstream effector and direct substrate of STEP is extracellular signal-regulated protein kinase (ERK), which has important functions in spine stabilisation and action potential transmission. The inhibition of STEP activity toward phospho-ERK has the potential to treat neuronal diseases, but the detailed mechanism underlying the dephosphorylation of phospho-ERK by STEP is not known. Therefore, we examined STEP activity toward para-nitrophenyl phosphate, phospho-tyrosine-containing peptides, and the full-length phospho-ERK protein using STEP mutants with different structural features. STEP was found to be a highly efficient ERK tyrosine phosphatase that required both its N-terminal regulatory region and key residues in its active site. Specifically, both kinase interaction motif (KIM) and kinase-specific sequence of STEP were required for ERK interaction. In addition to the N-terminal kinase-specific sequence region, S245, hydrophobic residues L249/L251, and basic residues R242/R243 located in the KIM region were important in controlling STEP activity toward phospho-ERK. Further kinetic experiments revealed subtle structural differences between STEP and HePTP that affected the interactions of their KIMs with ERK. Moreover, STEP recognised specific positions of a phospho-ERK peptide sequence through its active site, and the contact of STEP F311 with phospho-ERK V205 and T207 were crucial interactions. Taken together, our results not only provide the information for interactions between ERK and STEP, but will also help in the development of specific strategies to target STEP-ERK recognition, which could serve as a potential therapy for neurological disorders. Regulation of phospho-ERK by STEP underlies important neuronal activities. A detailed enzymologic characterisation and cellular studies of STEP revealed that specific residues in KIM and active site mediated ERK recognition. Structural differences between the KIM-ERK interfaces and the active site among different ERK phosphatases could be targeted to develop specific STEP inhibitor, which has therapeutic potential for neurological disorders. PKA, protein kinase A & NGF, nerve growth factor.