p38γ MAPK Inflammatory and Metabolic Signaling in Physiology and Disease.

p38γ MAPK (also called ERK6 or SAPK3) is a family member of stress-activated MAPKs and has common and specific roles as compared to other p38 proteins in signal transduction. Recent studies showed that, in addition to inflammation, p38γ metabolic signaling is involved in physiological exercise and in pathogenesis of cancer, diabetes, and Alzheimer's disease, indicating its potential as a therapeutic target. p38γphosphorylates at least 19 substrates through which p38γ activity is further modified to regulate life-important cellular processes such as proliferation, differentiation, cell death, and transformation, thereby impacting biological outcomes of p38γ-driven pathogenesis. P38γ signaling is characterized by its unique reciprocal regulation with its specific phosphatase PTPH1 and by its direct binding to promoter DNAs, leading to transcriptional activation of targets including cancer-like stem cell drivers. This paper will review recent findings about p38γ inflammation and metabolic signaling in physiology and diseases. Moreover, we will discuss the progress in the development of p38γ-specific pharmacological inhibitors for therapeutic intervention in disease prevention and treatment by targeting the p38γ signaling network.

Isoform-specific and cell/tissue-dependent effects of p38 MAPKs in regulating inflammation and inflammation-associated oncogenesis.

p38 MAPK (mitogen-activated protein kinases) family proteins (α, ß, γ and δ) are key inflammatory kinases and play an important role in relaying and processing intrinsic and extrinsic signals in response to inflammation, stress, and oncogene to regulate cell growth, cell death and cell transformation. Recent studies in genetic mouse models revealed that p38α in epithelial cells mostly suppresses whereas in immune cells it promotes inflammation and inflammation-associated oncogenesis. On the contrary, p38γ and p38δ signaling in immune and epithelial cells is both pro-inflammatory and oncogenic. This review summarizes recent discoveries in this field, discusses possible associated mechanisms, and highlights potentials of systemically targeting isoform-specific p38 MAPKs. Understanding of p38 MAPK isoform-specific and cell/tissue- and perhaps stage-dependent effects and their integrated regulated activity in inflammation and in inflammation-associated oncogenesis is essential for effectively targeting this group of kinases for therapeutic intervention.

p38γ MAPK Is Essential for Aerobic Glycolysis and Pancreatic Tumorigenesis.

KRAS is mutated in most pancreatic ductal adenocarcinomas (PDAC) and yet remains undruggable. Here, we report that p38γ MAPK, which promotes PDAC tumorigenesis by linking KRAS signaling and aerobic glycolysis (also called the Warburg effect), is a novel therapeutic target. p38γ interacted with a glycolytic activator PFKFB3 that was dependent on mutated KRAS. KRAS transformation and overexpression of p38γ increased expression of PFKFB3 and glucose transporter GLUT2, conversely, silencing mutant KRAS, and p38γ decreased PFKFB3 and GLUT2 expression. p38γ phosphorylated PFKFB3 at S467, stabilized PFKFB3, and promoted their interaction with GLUT2. Pancreatic knockout of p38γ decreased p-PFKFB3/PFKFB3/GLUT2 protein levels, reduced aerobic glycolysis, and inhibited PDAC tumorigenesis in KPC mice. PFKFB3 and GLUT2 depended on p38γ to stimulate glycolysis and PDAC growth and p38γ required PFKFB3/S467 to promote these activities. A p38γ inhibitor cooperated with a PFKFB3 inhibitor to blunt aerobic glycolysis and PDAC growth, which was dependent on p38γ. Moreover, overexpression of p38γ, p-PFKFB3, PFKFB3, and GLUT2 in PDAC predicted poor clinical prognosis. These results indicate that p38γ links KRAS oncogene signaling and aerobic glycolysis to promote pancreatic tumorigenesis through PFKFB3 and GLUT2, and that p38γ and PFKFB3 may be targeted for therapeutic intervention in PDAC. SIGNIFICANCE: These findings show that p38γ links KRAS oncogene signaling and the Warburg effect through PFKBF3 and Glut2 to promote pancreatic tumorigenesis, which can be disrupted via inhibition of p38γ and PFKFB3.

Targeting an oncogenic kinase/phosphatase signaling network for cancer therapy.

Protein kinases and phosphatases signal by phosphorylation and dephosphorylation to precisely control the activities of their individual and common substrates for a coordinated cellular outcome. In many situations, a kinase/phosphatase complex signals dynamically in time and space through their reciprocal regulations and their cooperative actions on a substrate. This complex may be essential for malignant transformation and progression and can therefore be considered as a target for therapeutic intervention. p38γ is a unique MAPK family member that contains a PDZ motif at its C-terminus and interacts with a PDZ domain-containing protein tyrosine phosphatase PTPH1. This PDZ-coupled binding is required for both PTPH1 dephosphorylation and inactivation of p38γ and for p38γ phosphorylation and activation of PTPH1. Moreover, the p38γ/PTPH1 complex can further regulate their substrates phosphorylation and dephosphorylation, which impacts Ras transformation, malignant growth and progression, and therapeutic response. This review will use the p38γ/PTPH1 signaling network as an example to discuss the potential of targeting the kinase/phosphatase signaling complex for development of novel targeted cancer therapy.

The K-Ras effector p38γ MAPK confers intrinsic resistance to tyrosine kinase inhibitors by stimulating EGFR transcription and EGFR dephosphorylation.

Mutations in K-Ras and epidermal growth factor receptor (EGFR) are mutually exclusive, but it is not known how K-Ras activation inactivates EGFR, leading to resistance of cancer cells to anti-EGFR therapy. Here, we report that the K-Ras effector p38γ MAPK confers intrinsic resistance to small molecular tyrosine kinase inhibitors (TKIs) by concurrently stimulating EGFR gene transcription and protein dephosphorylation. We found that p38γ increases EGFR transcription by c-Jun-mediated promoter binding and stimulates EGFR dephosphorylation via activation of protein-tyrosine phosphatase H1 (PTPH1). Silencing the p38γ/c-Jun/PTPH1 signaling network increased sensitivities to TKIs in K-Ras mutant cells in which EGFR knockdown inhibited growth. Similar results were obtained with the p38γ-specific pharmacological inhibitor pirfenidone. These results indicate that in K-Ras mutant cancers, EGFR activity is regulated by the p38γ/c-Jun/PTPH1 signaling network, whose disruption may be a novel strategy to restore the sensitivity to TKIs.

[Evaluation of the rapid trehalose test for the identification of the Candida glabrata].

OBJECTIVE: To explore a rapid and cost-effective method for identification of Candida glabrata through the comparison of two different methods, using molecular methods of sequencing as gold standard. METHODS: From our clinic, 200 strains of suspected Candida glabrata were collected during the last 3 years and selected after incubation in CHROMagar Candida medium for 48 h. By comparing the results of the CHROMagar Candida medium, the identification of the rapid trehalose test for different kinds of strains were analyzed under incubation in the tubes for 3 h, 6 h, and 24 h at 37 °C and 42 °C, respectively. All the strains were identified to species level by methods of sequencing. The optimal time and temperature of the trehalose test for the identification of Candida glabrata were assessed. Two different methods, CHROMagar Candida medium and the rapid trehalose test, in identification of Candida glabrata were compared. RESULTS: In all the 200 strains, Candida glabrata ferment trehalose with 3 h incubation under 42 °C were the optimal time and temperature for fermenting trehalose. The accuracy, sensitivity, and specificity of the rapid trehalose test were 99.00% (198/200), 98.66% (147/149) and 100.00% (51/51). The accuracy rate of CHROMagar Candida medium was 79.50% (159/200), the sensitivity and specificity were only 89.93% (134/149) and 49.02% (25/51), however, compared with the domestic current popular methods, the rapid trehalose test had better time efficiency ratio. CONCLUSION: The evaluation results suggest that the rapid trehalose test has advantages in terms of operational convenience and low cost, and the results can be obtained in 3 h. Therefore, it has application value in clinical laboratory.

p38gamma MAPK cooperates with c-Jun in trans-activating matrix metalloproteinase 9.

Mitogen-activated protein kinases (MAPKs) regulate gene expression through transcription factors. However, the precise mechanisms in this critical signal event are largely unknown. Here, we show that the transcription factor c-Jun is activated by p38gamma MAPK, and the activated c-Jun then recruits p38gamma as a cofactor into the matrix metalloproteinase 9 (MMP9) promoter to induce its trans-activation and cell invasion. This signaling event was initiated by hyperexpressed p38gamma that led to increased c-Jun synthesis, MMP9 transcription, and MMP9-dependent invasion through p38gamma interacting with c-Jun. p38gamma requires phosphorylation and its C terminus to bind c-Jun, whereas both c-Jun and p38gamma are required for the trans-activation of MMP9. The active p38gamma/c-Jun/MMP9 pathway also exists in human colon cancer, and there is a coupling of increased p38gamma and MMP9 expression in the primary tissues. These results reveal a new paradigm in which a MAPK acts both as an activator and a cofactor of a transcription factor to regulate gene expression leading to an invasive response.

PTPH1 dephosphorylates and cooperates with p38gamma MAPK to increase ras oncogenesis through PDZ-mediated interaction.

Protein phosphatases are believed to coordinate with kinases to execute biological functions, but examples of such integrated activities, however, are still missing. In this report, we have identified protein tyrosine phosphatase H1 (PTPH1) as a specific phosphatase for p38gamma mitogen-activated protein kinase (MAPK) and shown their cooperative oncogenic activity through direct binding. p38gamma, a Ras effector known to act independent of its phosphorylation, was first shown to require its unique PDZ-binding motif to increase Ras transformation. Yeast two-hybrid screening and in vitro and in vivo analyses further identified PTPH1 as a specific p38gamma phosphatase through PDZ-mediated binding. Additional experiments showed that PTPH1 itself plays a role in Ras-dependent malignant growth in vitro and/or in mice by a mechanism depending on its p38gamma-binding activity. Moreover, Ras increases both p38gamma and PTPH1 protein expression and there is a coupling of increased p38gamma and PTPH1 protein expression in primary colon cancer tissues. These results reveal a coordinative oncogenic activity of a MAPK with its specific phosphatase and suggest that PDZ-mediated p38gamma/PTPH1 complex may be a novel target for Ras-dependent malignancies.

[Study on the association between gestational diabetes mellitus and tumor necrosis factor-alpha gene polymorphism].

OBJECTIVE: To study allelic frequency of tumor necrosis factor-alpha (TNF-alpha) in gestational diabetes mellitus (GDM) of Han ethnicity in north China and to determine whether there is a specific allele of TNF-alpha associated with GDM susceptibility. METHODS: By using PCR-RFLP, we detected the distribution of TNF-alpha promoter alleles frequency in GDM women and control normal pregnant women. Plasma TNF-alpha levels and insulin levels were measured by radioimmunoassay. RESULTS: (1) There was a significant increase of A alleles frequency of TNF-alpha promoter -308 gene in GDM women compared with control group (61.4% vs 30.0%, P < 0.05) and an increase of the AA + GA genotype was observed in GDM group (71.4% vs 37.1%, P < 0.05). (2) In GDM group, the patients carrying the AA + GA genotype had higher plasma TNF-alpha levels (52 +/- 13 vs 14 +/- 4, P < 0.05) and a lower insulin sensitivity (13.6 +/- 6.5 vs 1.9 +/- 0.2, P < 0.05) compared with those carrying the other genotype (GG). CONCLUSIONS: The 308 G-->A polymorphism of TNF-alpha promoter gene is involved in the pathophysiology of insulin resistance and gestational diabetes mellitus.

[Study on association between gestational diabetes mellitus and sulfonylurea receptor-1 gene polymorphism].

OBJECTIVE: To investigate allelic frequency of sulfonylurea receptor-1 (SUR1) in gestational diabetes mellitus (GDM) women of Han nationality in north China in order to find out susceptible gene associated with GDM, and to assess the association between SUR1 allele and body mass index (BMI) and secretion of insulin. METHODS: Seventy cases of pregnant women were selected. It included 35 cases of pregnant women with GDM (GDM group), 35 cases of normal pregnant women (normal control group). Another 35 women patients with type 2 diabetes in the same period as T2DM group. By using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), we detected the distribution of SUR1 alleles frequency in all individuals of three groups. We also examined BMI, fasting insulin (INS(0)) and 2 h insulin levels (INS(120)). RESULTS: There was significantly increased c alleles frequency of SUR1 in GDM and T2DM women compared with normal pregnancy (70.0%, 71.4% and 52.9%, P < 0.05). Also significantly increased A alleles frequency of SUR1 in GDM and T2DM women was found compared with normal pregnancy (41.4%, 44.3% and 24.3%, P < 0.05). In GDM group, women carrying cc genotype had a higher BMI [(29.2 +/- 5.6) kg/m(2)], INS(0) [(14.9 +/- 8.7) mU/L] and INS(120) [(40.2 +/- 12.1) mU/L] as compared with those in carriers of other genotypes (ct and tt) (all P < 0.05). Also they had a lower insulin sensitivity (HOMA-IR) (3.9 +/- 2.5) as compared with carriers of ct genotype. Women carrying AA genotype had a higher INS(0) as compared with carriers of other genotypes (AG and GG) [(15.4 +/- 3.2), (12.1 +/- 4.5) and (11.5 +/- 4.8) mU/L, both P < 0.05]. Logistic regression analysis showed there was relationship between SUR1 cc genotype and severity of GDM (P = 0.005, RR = 25.128). CONCLUSIONS: There are -3t-->c and A/G polymorphism of SUR1 gene in the Han nationality. Alleles c of SUR1 are significantly implicated in the susceptibility to GDM. It suggests that the defect in SUR1 gene (cc and AA) may contribute to insulin hypersecretion, which might be the cause of increased body weight and decreased insulin sensitivity and genotype cc of SUR1 is connected with severe type of GDM. It might be the predictable index of GDM conversion to type 2 diabetes.