Distinct types of abnormality in kinetic properties of three Darier disease-causing sarco(endo)plasmic reticulum Ca2+-ATPase mutants that exhibit normal expression and high Ca2+ transport activity
Distinct types of abnormality in kinetic properties of three Darier disease-causing sarco(endo)plasmic reticulum Ca2+-ATPase mutants that exhibit normal expression and high Ca2+ transport activity
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DOI：
10.1074/jbc.m404887200
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发表时间：
2004-08-20
影响因子：
4.8
通讯作者：
Suzuki, H
中科院分区：
文献类型：
--
作者：
Sato, K;Yamasaki, K;Suzuki, H
探讨了三种不同的导致 Darier 病的 Ca2+-ATPase (SERCA2b) 突变体可能的功能异常：Ile(274) --> M3 腔端的 Val、Leu(321) --> Phe 在 M4 的细胞质部分和 Met(719) --> P 结构域中的 Ile，因为它们在 COS-1 细胞中表现出接近正常的表达和定位，以及高 ATPase 和耦合的 Ca2+ 转运活性与野生型相比，这些结果基本相同（L321F）或稍低（I274V 大约 35%，M719I 大约 30%）。这些突变恰好出现在我们之前发现的日本患者中。动力学分析表明，每个突变体都具有不同类型的异常。 M719I 和 L321F 对细胞质 Ca2+ 的亲和力降低了 2-3 倍，而 I274V 则具有正常的高亲和力。 L321F 还表现出对累积的腔内 Ca2+ 对运输循环的反馈抑制的敏感性显着降低，如 Ca2+ 离子载体对 ATP 酶活性的影响，更具体地说，Ca2+（高达 50 mM）对磷酸酶中间体衰变的影响所证明的。 I274V 和 M719I 的结果表明，为了避免单倍体不足，角质形成细胞中 Ca2+ 稳态的生理要求非常严格，可能比之前考虑的要严格得多。 L321F 对管腔 Ca2+ 不敏感可能导致管腔 Ca2+ 达到异常升高的水平。因此，这三种突变体具有独特的动力学特性改变，可能会导致细胞内 Ca2+ 稳态的不同类型的扰动，但尽管如此，所有类型的扰动都会导致 Darier 病。观察到的 L321F 的独特特征可能与该突变家系中的特定症状、神经精神障碍和行为问题有关。这些结果还进一步深入了解了 ATP 驱动的 Ca2+ 运输 SERCA 构象变化的整体性质。
The possible functional abnormalities in three different Darier disease-causing Ca2+-ATPase (SERCA2b) mutants, Ile(274) --> Val at the lumenal end of M3, Leu(321) --> Phe on the cytoplasmic part of M4, and Met(719) --> Ile in P domain, were explored, because they exhibited nearly normal expression and localization in COS-1 cells and the high ATPase and coupled Ca2+ transport activities that were essentially identical (L321F) or slightly lower (I274V by similar to35% and M719I by similar to30%) as compared with those of the wild type. These mutations happened to be in Japanese patients found previously by us. Kinetic analyses revealed that each of the mutants possesses distinct types of abnormalities; M719I and L321F possess the 2-3-fold reduced affinity for cytoplasmic Ca2+, whereas I274V possesses the normal high affinity. L321F exhibited also the remarkably reduced sensitivity to the feedback inhibition of the transport cycle by accumulated lumenal Ca2+, as demonstrated with the effect of Ca2+ ionophore on ATPase activity and more specifically with the effects of Ca2+ (up to 50 mM) on the decay of phosphoenzyme intermediates. The results on I274V and M719I suggest that the physiological requirement for Ca2+ homeostasis in keratinocytes to avoid haploinsufficiency is very strict, probably much more than considered previously. The insensitivity to lumenal Ca2+ in L321F likely brings the lumenal Ca2+ to an abnormally elevated level. The three mutants with their distinctively altered kinetic properties will thus likely cause different types of perturbation of intracellular Ca2+ homeostasis, but nevertheless all types of perturbation result in Darier disease. It might be possible that the observed unique feature of L321F could possibly be associated with the specific symptoms in the pedigree with this mutation, neuropsychiatric disorder, and behavior problems. The results also provided further insight into the global nature of conformational changes of SERCAs for ATP-driven Ca2+ transport.