Mechanistic investigations have shown that, upon agonist activation, hydroxy-carboxylic acid receptor-1(HCA1) couples to a Gi protein and inhibits adenylate cyclase activity, leading to inhibition of liberation of free fatty acid. However, the underlying molecular mechanisms for HCA1 signaling remain largely unknown. Using CHO-K1 cells stably expressing HCA1, and L6 cells, which endogenously express rat HCA1 receptors, we found that activation of ERK1/2 by HCA1 was rapid, peaking at 5 min, and was significantly blocked by pertussis toxin. Furthermore, time course experiments with different kinase inhibitors demonstrated that HCA1 induced ERK1/2 activation via the extracellular Ca2+, PKC and IGF-I receptor transactivation-dependent pathways. In addition, we observed that pretreated the cells with M119K, an inhibitor of Gβγ subunit-dependent signaling, effectively attenuated the ERK1/2 activation triggered by HCA1, suggesting a critical role for βγ-subunits in HCA1-activated ERK1/2 phosphorylation. Furthermore, the present results also indicated that the arrestin2/3 were not required for ERK1/2 activation. In conclusion, our findings demonstrate that upon binding to agonist, HCA1 receptors initially activate Gi, leading to dissociation of the Gβγ subunit from activated Gi, and subsequently induce ERK1/2 activation via two distinct pathways: one PKC-dependent pathway and the other IGF-IR transactivation-dependent pathway. Our results provide the first in-depth evidence that defines the molecular mechanism of HCA1-mediated ERK1/2 activation.
In order to seek the feasibility of freshness prediction ofLing-Wulong jujubes based on dielectric spectrum, the electrical parameters ofLing-Wulong jujube were measured dynamically using HIOKI 3532-50 LCR parallel-plates measuring instrument. The concept of dielectric freshness F was put forward and its freshness index TI was proposed according to local standards. The results indicated that there was significant linear correlation between F value and TI (R2=0.709). The freshness prediction model ofLing-Wulong jujubes was established using the BP - ANN neural network (R2=0.894), the grade recognition rate was up to 82.14%. Freshness prediction of postharvestLing-Wulong jujubes based on its dielectric spectrum was feasible.
In order to detect Lingwu long jujube quality, the electrical parameters of Lingwu long-Jujube picked and stored at room temperature were measured dynamically with parallel plate measuring instrument HIOKI 3532-50 LCR. The variation of quality indicators such as pulp firmness, brittleness, total soluble solid (TSS) and moisture during storage were tested and analyzed. Regression equations of quality and under five appropriate test frequencies were established. Among the five test frequencies, 3.16 kHz was determined as the characteristic frequency. The results showed there is a strong correlation between long-Jujube quality and under the characteristic frequency. The method could be used for the jujube fruit quality detection, and can be extended to other fruits quality detection also.
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