Schmidt Albrecht G, Zhai Jing, Carr Andrew N, Gerst Mike J, Lorenz John N, Pollesello Piero, Annila Arto, Hoit Brian D, Kranias Evangelia G
Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267-0575, USA.
Cardiovasc Res. 2002 Nov;56(2):248-59. doi: 10.1016/s0008-6363(02)00541-2.
The role of sarcoplasmic reticulum (SR) in the onset and progression of heart failure is controversial. We tested the hypothesis that impairment of SR Ca2+ sequestration may be a primary cause for progressive left ventricular (LV) dysfunction and the phospholamban hinge domain may be critical in this process.
A phospholamban hinge domain mutant (PLB/N27A) was introduced in the cardiac compartment of the phospholamban null mouse. An integrative approach was used to characterize the resulting cardiac phenotype at a structural, cellular, whole organ and intact animal level.
NMR analysis revealed a defined alteration in the alpha-helical configuration between residues Q22 to F35 in mutant phospholamban. Transgenic lines expressing similar levels of mutant compared to wild-type phospholamban exhibited super-inhibition of the SR Ca2+ ATPase affinity for Ca2+ (EC50 0.52 microM) in oxalate-supported Ca2+ uptake measurements, which translated into impaired relaxation and attenuated responses to beta-adrenergic stimulation. Importantly, a blunted force-frequency relation was observed in mutant hearts preceding left ventricular dilation. Upon aging to 10 months, the predominantly diastolic dysfunction progressed to congestive heart failure, characterized by induction of a fetal gene program, cardiac remodeling, lung congestion, depressed systolic function and early mortality.
Increased inhibition of Ca2+ sequestration may be a causative factor in the development of left ventricular dysfunction and myocyte remodeling leading to heart failure. Furthermore, the hinge domain may play an important role in transmitting PLB's regulatory effects on SERCA.
肌浆网（SR）在心力衰竭的发生和发展中的作用存在争议。我们检验了以下假设，即SR钙摄取受损可能是左心室（LV）功能进行性障碍的主要原因，而受磷蛋白铰链区在此过程中可能起关键作用。
将受磷蛋白铰链区突变体（PLB/N27A）导入受磷蛋白基因敲除小鼠的心脏区域。采用综合方法在结构、细胞、全器官和完整动物水平上对由此产生的心脏表型进行表征。
核磁共振分析显示突变型受磷蛋白中第22位至第35位残基之间的α-螺旋结构发生了明确改变。与野生型受磷蛋白表达水平相似的转基因品系在草酸盐支持的钙摄取测量中表现出对SR钙ATP酶对钙的亲和力的超抑制（EC50为0.52微摩尔），这转化为舒张功能受损和对β-肾上腺素能刺激的反应减弱。重要的是，在左心室扩张之前，突变型心脏中观察到力-频率关系减弱。到10个月龄时，主要的舒张功能障碍发展为充血性心力衰竭，其特征为诱导胎儿基因程序、心脏重塑、肺充血、收缩功能降低和早期死亡。
钙摄取抑制增加可能是导致左心室功能障碍和心肌细胞重塑进而导致心力衰竭的一个致病因素。此外，铰链区可能在传递受磷蛋白对肌浆网钙ATP酶的调节作用中起重要作用。
