抗钠-钙交换体α-1重复序列(117-137)抗体对心肌钠-钙交换电流及钙电流的抑制作用(英文)

Inhibitory effects of purified antibody against α-1 repeat(117-137) on Na^+-Ca^(2+) exchange and L-type Ca^(2+) currents in rat cardiomyocytes

本研究旨在探讨抗钠-钙交换体(Na+-Ca2+ exchanger,NCX)α-1重复序列(117-137)抗体对大鼠心肌细胞钠-钙交换电流的影响。实验用合成的α-1重复序列(117-137)肽免疫大鼠制备抗α-1重复序列(117-137)抗体;应用全细胞膜片钳技术,在急性分离的心肌细胞上观察抗α-1重复序列(117-137)抗体对大鼠心肌细胞钠-钙交换电流的影响,同时还观察了其对大鼠心肌细胞L型钙通道、电压门控钠通道和豚鼠心肌延迟整流钾通道电流的影响;最后,采用EMBOSS Pairwise Alignment Algorithms软件对NCXα-1重复序列和L型钙通道(1076～1096)的氨基酸序列进行了比较。结果显示,抗α-1重复序列(117-137)抗体对大鼠心肌细胞Na+-Ca2+交换电流呈现剂量依赖性的抑制作用。在钳制电压为+50和-100mV时,其抑制外向和内向钠-钙交换电流的IC50分别为18.9和22.4nmol/L。此外,该抗体还对L型钙通道电流具有抑制效应(IC50=22.7nmol/L),对电压门控钠通道和延迟整流钾通道电流则无明显影响。通过氨基酸序列比对发现,NCX α-1重复序列(117-137)与L型钙通道IIIS5-S6序列(孔环)之间具有23.8%的相似性。以上结果表明,抗NCX α-1重复序列(117-137)抗体是心肌NCX的一种抑制性抗体,同时也可以抑制L型钙通道。

Considering that α-1 repeat region may be involved in the ion binding and translocation of Na＋-Ca2＋ exchanger（NCX）,it is possible that the antibodies against NCX α-1 repeat may have a crucial action on NCX activity.The aim of the present study is to investigate the effect of antibody against α-1 repeat（117-137）,designated as α-1（117-137）,on NCX activity.The antibody against the synthesized α-1（117-137） was prepared and affinity-purified.Whole-cell patch clamp technique was used to study the change of Na＋Ca2＋ exchange current（INa/Ca） in adult rat cardiomyocytes.To evaluate the functional specificity of this antibody,its effects on L-type Ca2＋ current（ICa,L）,voltage-gated Na＋ current（INa） and delayed rectifier K＋ current（IK） were also observed.The amino acid sequences of α-1（117-137） in NCX and residues 1 076-1 096 within L-type Ca2＋ channel were compared using EMBOSS Pairwise Alignment Algorithms.The results showed that outward and inward INa/Ca were decreased by the antibody against α-1（117-137） dose-dependently in the concentration range from 10 to 160 nmol/L,with IC50 values of 18.9 nmol/L and 22.4 nmol/L,respectively.Meanwhile,the antibody also decreased ICa,L in a concentration-dependent manner with IC50 of 22.7 nmol/L.No obvious effects of the antibody on INa and IK were observed.Moreover,comparison of the amino acid sequences showed there was 23.8% sequence similarity between NCX α-1（117-137） and residues 1 076-1 096 within L-type Ca2＋ channel.These results suggest that antibody against α-1（117-137） is a blocking antibody to NCX and can also decrease ICa,L in a concentration-dependent manner,while it does not have obvious effects on INa and IK.