Sepúlveda M Rosario, Berrocal-Carrillo María, Gasset María, Mata Ana M
Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, Avda de Elvas s/n, 06071 Badajoz, Spain.
J Biol Chem. 2006 Jan 6;281(1):447-53. doi: 10.1074/jbc.M506950200. Epub 2005 Oct 25.
Here we describe the association of the synaptosomal plasma membrane Ca2+-ATPase (PMCA) from pig cerebellum with cholesterol/sphingomyelin-rich membrane domains (rafts). The PMCA4 was localized exclusively in rafts prepared by flotation in Nycodenz density gradients of ice-cold Brij 96 extracts. This was corroborated by its colocalization with the raft markers cholesterol, ganglioside GM1, and PrP(C). The remaining PMCA isoforms were found in the detergent-soluble fractions, with the majority of the membrane proteins. Activity assays confirmed the bimodal distribution of the PMCA isoforms in the density gradient, with a lower activity for PMCA4 and greater stimulation by calmodulin than for the other isoforms. By providing an ordered membrane microenvironment, lipid rafts may contribute to the interaction of PMCA4 with proteins involved in Ca2+ signaling at discrete functional positions on the synaptic nerve terminals.
在此，我们描述了猪小脑突触体血浆膜Ca2+ -ATP酶（PMCA）与富含胆固醇/鞘磷脂的膜结构域（脂筏）之间的关联。PMCA4仅定位于通过在冰冷的Brij 96提取物的Nycodenz密度梯度中浮选制备的脂筏中。这通过其与脂筏标志物胆固醇、神经节苷脂GM1和PrP(C)的共定位得到了证实。其余的PMCA同工型存在于去污剂可溶部分中，与大多数膜蛋白一起。活性测定证实了PMCA同工型在密度梯度中的双峰分布，PMCA4的活性较低，并且与其他同工型相比，钙调蛋白对其的刺激作用更大。通过提供有序的膜微环境，脂筏可能有助于PMCA4与突触神经末梢离散功能位置上参与Ca2+信号传导的蛋白质相互作用。
