Lipid lateral heterogeneity in phosphatidylcholine/phosphatidylserine/diacylglycerol vesicles and its influence on protein kinase C activation
Lipid lateral heterogeneity in phosphatidylcholine/phosphatidylserine/diacylglycerol vesicles and its influence on protein kinase C activation
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DOI：
10.1016/s0006-3495(96)79387-6
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发表时间：
1996-10-01
影响因子：
3.4
通讯作者：
Biltonen, RL
中科院分区：
文献类型：
--
作者：
Dibble, ARG;Hinderliter, AK;Biltonen, RL
为了验证蛋白激酶C（PKC）的激活受脂质双层组分的横向异质性影响的假设，比较了二肉豆蔻酰磷脂酰胆碱（DMPC）/二肉豆蔻酰磷脂酰丝氨酸（DMPS）/二油酰甘油（DO）囊泡的热致相行为和该系统对PKC的激活。差示扫描量热法（DSC）和傅里叶变换红外（FTIR）光谱用于监测主转变（即，凝胶-流体相变）作为DMPC/DO、DMPS/DO和[DMPC/DMPS（1：1，mol/mol）]/DO多层囊泡（MLV）中摩尔分数DO（chi（DO））的函数。在每种情况下，当chi（DO）<类似于0.3时，DO显着拓宽了主转变并将其转移到较低的温度;但当chi（DO）>类似于0.3时，主转变变得高度合作，即，又窄了。重叠的窄和宽转变的共存在DSC热谱图中是明显的，从chi（DO）近似0.1到chi（DO）近似0.3，随着chi（DO）的增加，更合作的转变以牺牲更宽的转变为代价而增长。FTIR光谱，使用类似物的DMPC和DMPS与全氘代的酰基链，表明所有三个脂质组分的熔融曲线在[DMPC/DMPS（1：1，mol/mol）]/DO MLV几乎重叠时，chi（DO）= 0.33，表明一种新的类型的相，与磷脂/DO摩尔比接近2：1，在这个系统中形成。总的来说，即使在高于主转变的温度下，结果也与整个组合物中贫DO和富DO域的共存一致，chi（DO）近似为0.1至chi（DO）近似为0.3。二元混合物的相行为与三元混合物的相行为的比较表明，DMPS/DO相互作用可能比DMPC/DO相互作用在三元体系中更有利，特别是在凝胶状态下。以[DMPC/DMPS（1：1，mol/mol）]/DO MLV为脂质激活剂测定PKC活性。在35 ℃（高于脂质主要转变的温度），PKC活性随着chi（DO）的增加而逐渐增加，从chi（DO）约0.1增加到chi（DO）约0.4，并且在较高的DO含量下活性保持较高。相反，在2 ℃（低于主要转变的温度），PKC活性在接近0.1的chi（DO）和接近0.3的chi（DO）之间表现出最大值，并且在较高DO含量下，活性基本上恒定在最大值时活性的20-25%。我们从这些结果推断，形成的DO丰富的域与PKC激活，当脂质在凝胶状态下，DO-穷人和DO-丰富的阶段的共存也有助于PKC激活。
To test the hypothesis that the activation of protein kinase C (PKC) is influenced by lateral heterogeneities of the components of the lipid bilayer, the thermotropic phase behavior of dimyristoylphosphatidylcholine (DMPC)/dimyristoylphosphatidylserine (DMPS)/dioleoylglycerol (DO) vesicles was compared with the activation of PKC by this system. Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy were used to monitor the main transition (i.e., the gel-to-fluid phase transition) as a function of mole fraction DO (chi(DO)) in DMPC/DO, DMPS/DO, and [DMPC/DMPS (1:1, mol/mol)]/DO multilamellar vesicles (MLVs). In each case, when chi(DO) < similar to 0.3, DO significantly broadened the main transition and shifted it to lower temperatures; but when chi(DO) > similar to 0.3, the main transition became highly cooperative, i.e., narrow, again. The coexistence of overlapping narrow and broad transitions was clearly evident in DSC thermograms from chi(DO) approximate to 0.1 to chi(DO) approximate to 0.3, with the more cooperative transition growing at the expense of the broader one as chi(DO) increased. FTIR spectroscopy, using analogs of DMPC and DMPS with perdeuterated acyl chains, showed that the melting profiles of all three lipid components in [DMPC/DMPS (1:1, mol/mol)]/DO MLVs virtually overlay when chi(DO) = 0.33, suggesting that a new type of phase, with a phospholipid/DO mole ratio near 2:1, is formed in this system. Collectively, the results are consistent with the coexistence of DO-poor and DO-rich domains throughout the compositions chi(DO) approximate to 0.1 to chi(DO) approximate to 0.3, even at temperatures above the main transition. Comparison of the phase behavior of the binary mixtures with that of the ternary mixtures suggests that DMPS/DO interactions may be more favorable than DMPC/DO interactions in the ternary system, especially in the gel state. PKC activity was measured using [DMPC/DMPS (1:1, mol/mol)]/DO MLVs as the lipid activator. At 35 degrees C (a temperature above the main transition of the lipids), PKC activity increased gradually with increasing chi(DO) from chi(DO) approximate to 0.1 to chi(DO) approximate to 0.4, and activity remained high at higher DO contents. In contrast, at 2 degrees C (a temperature below the main transition), PKC activity exhibited a maximum between chi(DO) approximate to 0.1 and chi(DO) approximate to 0.3, and at higher DO contents activity was essentially constant at 20-25% of the activity at the maximum. We infer from these results that the formation of DO-rich domains is related to PKC activation, and when the lipid is in the gel state, the coexistence of DO-poor and DO-rich phases also contributes to PKC activation.