BACKGROUND AND PURPOSE3-Hydroxy-octanoate, recently identified as a ligand for, the orphan GPCR, HCA3, is of particular interest given its ability to treat lipid disorders and atherosclerosis. Here we demonstrate the pathway of HCA3-mediated activation of ERK1/2. EXPERIMENTAL APPROACHUsing CHO-K1 cells stably expressing HCA3 receptors and A431 cells, a human epidermoid cell line with high levels of endogenous expression of functional HCA3 receptors, HCA3-mediated activation of ERK1/2 was measured by Western blot. KEY RESULTSHCA3-mediated activation of ERK1/2 was rapid, peaking at 5 min, and was Pertussis toxin sensitive. Our data, obtained by time course analyses in combination with different kinase inhibitors, demonstrated that on agonist stimulation, HCA3 receptors evoked ERK1/2 activation via two distinct pathways, the PLC/PKC pathway at early time points (Յ2 min) and the MMP/ epidermal growth factor receptor (EGFR) transactivation pathway with a maximum response at 5 min. Furthermore, our present results also indicated that the bg-subunits of the Gi protein play a critical role in HCA3-activated ERK1/2 phosphorylation, whereas b-arrestins and Src were not required for ERK1/2 activation. CONCLUSIONS AND IMPLICATIONSWe have described the molecular mechanisms underlying the coupling of human HCA3 receptors to the ERK1/2 MAP kinase pathway in CHO-K1 and A431 cells, which implicate the Gi protein-initiated, PLC/PKC-and platelet-derived growth factor receptor/EGFR transactivation-dependent pathways. These observations may provide new insights into the pharmacological effects and the physiological functions modulated by the HCA3-mediated activation of ERK1/2. AbbreviationsADAM, a disintegrin and metalloproteinase; CRE, cAMP response element; EGFR, epidermal growth factor receptor;

Docetaxel-based therapy is one of the first-line options for castration-resistant prostate cancer (CRPC). However, a large proportion of CRPC patients show different extents of docetaxel resistance. The current study aims to investigate the role of testicular nuclear receptor 4 (TR4) in docetaxel resistance in CRPC. TR4 expression level in prostate biopsy samples from CRPC patients treated with docetaxel was measured by immunohistochemistry (IHC). Alternation of TR4 expression in prostate cancer (PCa) cell line PC3 was applied to find out the influence of TR4 on half-maximal inhibitory concentration (IC50), cell viability and cell apoptosis. Patients who failed to achieve prostate-specific antigen (PSA) response (<50% PSA reduction from baseline) after docetaxel-based chemotherapy had a comparatively higher TR4 expression than those who achieved PSA response (⩾50% PSA reduction from baseline). Knocking down TR4 in PC3 cells led to a lower IC50 dose, poorer cell viability and more cell apoptosis when treated with docetaxel, whereas overexpression of TR4 in PC3 led to a higher IC50 dose, better cell viability and less cell apoptosis. TR4 enhances the chemo-resistance of docetaxel in CRPC. It may serve as a biomarker to determine the prognosis of docetaxel-based therapy and as a potential therapy target to combine with docetaxel to better suppress CRPC.

The target of the rapamycin (TOR) signaling pathway is highly conserved and important in eukaryotes. It is involved in the regulation of various biological processes. However, systematic studies on this pathway in the genus Aspergillus have not been reported. Here, we identified and characterized nine genes encoding components of the TOR pathway in A. flavus, and investigated their biological, genetic and biochemical functions. The FK506-binding protein FKBP3 and its lysine succinylation are important for aflatoxin production and rapamycin resistance. The Tor kinase plays a central role in the global regulation of growth, spore production, aflatoxin biosynthesis and rapamycin stress. As a major downstream effector molecule of Tor kinase, the Sch9 kinase might regulate the calcium and osmotic stress, AFB1 synthesis of A. flavus by its S_TKc, S_TK_X domains and ATP binding site at K340. We also showed that Sch9 kinase might mediate crosstalk between the TOR and the HOG signaling pathways. TapA and TipA, the other downstream components of Tor kinase, play important roles in regulating mycelial growth and sclerotia formation in A. flavus. The member of the TapA-phosphatase complexes Sit4 and Ppg1 are important for hyphal development, sexual reproduction, sclerotia formation, AFB1 biosynthesis, activation of the CWI and TOR signaling pathways in A. flavus. In addition, the another phosphatase complex Nem1/Spo7 play critical role in vegetative growth, conidiation, aflatoxin and LD biogenesis. This study provide new insights into constructing the regulatory network of the TOR signaling pathway and revealing the molecular mechanism of the pathogenicity in A. flavus.

The target of the rapamycin (TOR) signaling pathway is highly conserved and important in eukaryotes. It is involved in the regulation of various biological processes. However, systematic studies on this pathway in the genus Aspergillus have not been reported. Here, we identified and characterized nine genes encoding components of the TOR pathway in A. flavus, and investigated their biological, genetic and biochemical functions. The FK506-binding protein FKBP3 and its lysine succinylation are important for aflatoxin production and rapamycin resistance. The Tor kinase plays a central role in the global regulation of growth, spore production, aflatoxin biosynthesis and rapamycin stress. As a major downstream effector molecule of Tor kinase, the Sch9 kinase might regulate the calcium and osmotic stress, AFB1 synthesis of A. flavus by its S_TKc, S_TK_X domains and ATP binding site at K340. We also showed that Sch9 kinase might mediate crosstalk between the TOR and the HOG signaling pathways. TapA and TipA, the other downstream components of Tor kinase, play important roles in regulating mycelial growth and sclerotia formation in A. flavus. The member of the TapA-phosphatase complexes Sit4 and Ppg1 are important for hyphal development, sexual reproduction, sclerotia formation, AFB1 biosynthesis, activation of the CWI and TOR signaling pathways in A. flavus. In addition, the another phosphatase complex Nem1/Spo7 play critical role in vegetative growth, conidiation, aflatoxin and LD biogenesis. This study provide new insights into constructing the regulatory network of the TOR signaling pathway and revealing the molecular mechanism of the pathogenicity in A. flavus.

The target of the rapamycin (TOR) signaling pathway is highly conserved and important in eukaryotes. It is involved in the regulation of various biological processes. However, systematic studies on this pathway in the genus Aspergillus have not been reported. Here, we identified and characterized nine genes encoding components of the TOR pathway in A. flavus, and investigated their biological, genetic and biochemical functions. The FK506-binding protein FKBP3 and its lysine succinylation are important for aflatoxin production and rapamycin resistance. The Tor kinase plays a central role in the global regulation of growth, spore production, aflatoxin biosynthesis and rapamycin stress. As a major downstream effector molecule of Tor kinase, the Sch9 kinase might regulate the calcium and osmotic stress, AFB1 synthesis of A. flavus by its S_TKc, S_TK_X domains and ATP binding site at K340. We also showed that Sch9 kinase might mediate crosstalk between the TOR and the HOG signaling pathways. TapA and TipA, the other downstream components of Tor kinase, play important roles in regulating mycelial growth and sclerotia formation in A. flavus. The member of the TapA-phosphatase complexes Sit4 and Ppg1 are important for hyphal development, sexual reproduction, sclerotia formation, AFB1 biosynthesis, activation of the CWI and TOR signaling pathways in A. flavus. In addition, the another phosphatase complex Nem1/Spo7 play critical role in vegetative growth, conidiation, aflatoxin and LD biogenesis. This study provide new insights into constructing the regulatory network of the TOR signaling pathway and revealing the molecular mechanism of the pathogenicity in A. flavus.