Gosmanov A R, Thomason D B
Department of Physiology, College of Medicine, University of Tennessee Health Science Center, Memphis, USA.
Tsitologiia. 2003;45(8):812-6.
In mammalian cells, Na(+)-K(+)-2Cl- cotransporter activity participates in regulation of ion and volume homeostasis. This makes NKCC indispensable for normal cell growth and proliferation. We recently reported the existence of two mechanisms that can regulate NKCC activity in mature skeletal muscle. In isosmotic conditions, signaling through ERK MAPK pathway is necessary, while inhibition of the cAMP-dependent protein kinase A (PKA) pathway stimulates NKCC activity during hyperosmotic challenge. Both pathways are involved in regulating cell proliferation in wide variety of cells of epithelial and non-epithelial origin, so we tested which pathway regulated NKCC activity in cultured cells. In cultured rat skeletal muscle (L6) and intestinal epithelial (IEC-6) cells, NKCC activity in the basal state comprised 30 to 50% of total potassium influx, assessed as bumetanide-sensitive 38Rb-uptake. This NKCC activity could not be abolished by inhibitors of ERK MAPK (PD98059 and U0126), PKC (GF109203X), or PI 3-K (wortmannin, LY294002). In L6 myoblasts and in IEC-6 cells, elevation of cAMP levels with isoproterenol or forskolin led to a 60% inhibition on NKCC activity. In contrast, incubation of IEC-6 cells with the PKA-inhibitor H-89 resulted in 50% increase of NKCC activity compared with the basal level. In conclusion, it appears that in cultured cells the cAMP--PKA pathway regulates NKCC activity. This resembles hyperosmotic regulation of NKCC activity.
在哺乳动物细胞中，钠-钾-2氯协同转运蛋白活性参与离子和体积稳态的调节。这使得NKCC对于正常细胞生长和增殖不可或缺。我们最近报道了两种可调节成熟骨骼肌中NKCC活性的机制。在等渗条件下，通过ERK MAPK途径的信号传导是必要的，而在高渗刺激期间抑制cAMP依赖性蛋白激酶A（PKA）途径可刺激NKCC活性。这两条途径都参与调节多种上皮和非上皮来源细胞的细胞增殖，因此我们测试了哪条途径调节培养细胞中的NKCC活性。在培养的大鼠骨骼肌（L6）和肠上皮（IEC-6）细胞中，基础状态下的NKCC活性占总钾流入量的30%至50%，通过布美他尼敏感的38Rb摄取进行评估。这种NKCC活性不能被ERK MAPK抑制剂（PD98059和U0126）、PKC抑制剂（GF109203X）或PI 3-K抑制剂（渥曼青霉素、LY294002）消除。在L6成肌细胞和IEC-6细胞中，用异丙肾上腺素或福斯高林升高cAMP水平导致NKCC活性受到60%的抑制。相反，用PKA抑制剂H-89孵育IEC-6细胞导致NKCC活性比基础水平增加50%。总之，在培养细胞中，cAMP-PKA途径似乎调节NKCC活性。这类似于NKCC活性的高渗调节。
