Loo D D, Hirsch J R, Sarkar H K, Wright E M
Department of Physiology, UCLA School of Medicine, Center for the Health Sciences, Los Angeles, CA 90095-1751, USA.
FEBS Lett. 1996 Sep 2;392(3):250-4. doi: 10.1016/0014-5793(96)00823-x.
The goal was to investigate the role of protein kinases in modulating taurine transporter activity in Xenopus laevis oocytes expressing the mouse retinal Na+/C-/taurine transporter. The currents generated by the taurine transporter were studied with a two-electrode voltage clamp and we recorded the maximal current (Imax), presteady-state charge transfer Q, and membrane capacitance Cm. 8-Br-cAMP, a membrane-permeable activator of the cAMP-dependent protein kinase (PKA), decreased Imax (41%), Q (41%) and Cm (10%). Similarly, 1 microM sn-1,2-dioctanoylglycerol (DOG), an activator of the Ca2+/diacylglycerol-dependent protein kinase (PKC), decreased Imax (56%), Q (37%), and Cm (9%). Calyculin A, a specific inhibitor of protein phosphatases 1 and 2A, also produced effects similar to those of 8-Br-cAMP and DOG, and decreased Imax (64 %), Q (38%), and Cm (10%). We conclude that the taurine transporter is regulated by activators of PKA and PKC, and regulation occurs largely by changes in the number of transporters in the plasma membrane.
目的是研究蛋白激酶在调节表达小鼠视网膜Na⁺/Cl⁻/牛磺酸转运体的非洲爪蟾卵母细胞中牛磺酸转运体活性方面的作用。利用双电极电压钳研究牛磺酸转运体产生的电流，我们记录了最大电流（Imax）、稳态前电荷转移Q和膜电容Cm。8-溴-环磷酸腺苷（8-Br-cAMP），一种环磷酸腺苷依赖性蛋白激酶（PKA）的膜通透性激活剂，使Imax降低（41%）、Q降低（41%）以及Cm降低（10%）。同样，1微摩尔的sn-1,2-二辛酰甘油（DOG），一种Ca²⁺/二酰基甘油依赖性蛋白激酶（PKC）的激活剂，使Imax降低（56%）、Q降低（37%）以及Cm降低（9%）。花萼海绵诱癌素A，一种蛋白磷酸酶1和2A的特异性抑制剂，也产生了与8-Br-cAMP和DOG类似的效应，并使Imax降低（64%）、Q降低（38%）以及Cm降低（10%）。我们得出结论，牛磺酸转运体受PKA和PKC激活剂的调节，并且调节主要通过质膜中转运体数量的变化来实现。
