蛋白酶激活接受器一(protease-activated receptor 1)是一種G蛋白連結接受器 (G protein-coupled receptor)，能被凝血蛋白酶(thrombin)所激活。窖蛋白一(caveolin-1)已知參與多個G蛋白連結接受器之訊息調控。然而，目前並不知道窖蛋白一是否會參與調控蛋白酶激活接受器一的訊息傳遞。為了要研究窖蛋白一是否參與調控蛋白酶激活接受器一的訊息傳遞，利用小分子核酸干擾(small interfering RNA)阻礙窖蛋白一的表現，進而測試活化蛋白酶激活接受器一所導致之腺苷酸酸環化酶(adenylyl cyclase)及細胞外信號調節激酶(extracellular signal-regulated kinase)之活性變化。因為窖蛋白一的表現受到高度調控，首先使用蛋白質抑制劑放線菌酮(cycloheximide)進行窖蛋白一的半衰期測試。測試發現窖蛋白一的半衰期約四十八小時，而在七十二小時幾乎都降解完。另外已知細胞生長的密度也會影響窖蛋白一的表現，在小分子核酸干擾阻礙窖蛋白一的表現後，測試在不同的細胞密度下，窖蛋白一的表現是否有影響。發現細胞密度在百分之七十五以下，是小分子核酸干擾阻礙窖蛋白一表現之適合條件。當利用小分子核酸干擾方式阻礙窖蛋白一的表現，在蛋白酶激活接受器一活化下，發現腺苷酸酸環化酶的活化與窖蛋白一無關，而在沒有窖蛋白一下，細胞外信號調節激酶活性的持續會減弱。總結，在人類胚胎腎臟細胞(human embryonic kidney 293)內蛋白酶激活接受器一的訊息途徑中，窖蛋白一能延續細胞外信號調節激酶活性，但與腺苷酸酸環化酶的活化無關。

Protease-activated receptor 1 (PAR1), a G protein-coupled receptor (GPCR), is activated by thrombin. Recently, caveolin-1 has been found to be involved in the regulation of cell signaling of several GPCRs. However, it is still unknown whether caveolin-1 plays any role in PAR1 signaling. To determine whether caveolin-1 is involved in PAR1 signaling, I have examined the effect of caveolin-1 knockdown on adenylyl cyclase activity and extracellular signal-regulated kinase (ERK) activation induced by PAR1. Because the expression of caveolin-1 is highly regulated, the half-life of caveolin-1 was examined by the addition of cycloheximide to inhibit proteins synthesis. I found that the half-life of caveolin-1 is about 48 hours and caveolin-1 could be almost degraded in 72 hours. Since the cell confluency has been reported to influence the expression of caveolin-1, the expression of caveolin-1 at different cell confluency was also determined after applying small interfering RNA (siRNA) to knock down caveolin-1. It was found that the cell conflunecy should be below 75% as the optimal condition for caveolin-1 knockdown. By applying siRNA-mediated knockdown of caveolin-1, I found that after PAR1 activation, caveolin-1 is not involved in Gi-dependent inhibition of adenylyl cyclase and that loss of caveolin-1 attenuates the duration of ERK activation induced by PAR1. The results indicate that caveolin-1 extends the duration of ERK activation but not regulates Gi-dependent inhibition of adenylyl cyclase induced by PAR1 in HEK 293 cells.

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