Acidification of three types of liver endocytic vesicles: similarities and differences.
Acidification of three types of liver endocytic vesicles: similarities and differences.
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DOI：
10.1152/ajpcell.1994.266.1.c81
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
R. V. Dyke;J. Belcher
中科院分区：
文献类型：
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作者：
R. V. Dyke;J. Belcher
内吞配体通过一系列酸性逐渐增强的囊泡移动。这些pH （pHi）的差异可能反映了离子传输机制的差异。囊泡代表了三个阶段的内噬作用，受体和配体解偶联室（CURL），多泡体（MVB）和受体回收室（RRC），并且都表现出atp依赖性的电致酸化，这是介质氯化物的饱和功能。酸化的初始速率不同（RRC > CURL > MVB）， CURL和RRC的质子内流相似，但MVB的质子内流较慢。三个囊泡中atp依赖的稳态pHi更为相似。在低氯介质中，囊泡膜电位较大（+41 ~ +69 mV）， RRC最大，但在140 mM KCl中，囊泡膜电位较低（-6 ~ +6 mV）。这些囊泡也表现出-22 ~ -37 mV的Donnan电位。稳态泵浦产生的质子电化学梯度（δ μ H+）在114 ~ 175 mV之间，旋度和RRC比MVB更大；然而，H+变化不大，氯离子浓度相差140倍。在CURL和RRC中质子泄漏速率比MVB快，但质子流出相似。最后，质子通量和渗透率，计算有关的表面积，在相反的方向不同（MVB >旋度> RRC）。因此，对于所研究的内吞囊泡，可以证明质子通量和囊泡几何形状的内在差异导致了预稳态囊泡pHi的差异。
Endocytosed ligands move through a series of progressively more acidic vesicles. These differences in pH (pHi) could reflect differences in ion transport mechanisms. Vesicles representing three stages of endocytosis, compartment for uncoupling of receptor and ligand (CURL), multivesicular bodies (MVB), and receptor recycling compartment (RRC), were studied, and all exhibited ATP-dependent electrogenic acidification that was a saturable function of medium chloride. Initial rates of acidification differed (RRC > CURL > MVB), and proton influx was similar for CURL and RRC but slower for MVB. Steady-state ATP-dependent pHi in the three vesicles was more similar. Vesicle membrane potential was substantial (+41 to +69 mV) in low-chloride medium and greatest for RRC but was low (-6 to +6 mV) in 140 mM KCl. These vesicles also exhibited -22 to -37 mV Donnan potentials. Steady-state pump-generated proton electrochemical gradients (delta mu H+) ranged from 114 to 175 mV and were greater for CURL and RRC than for MVB; however, delta mu H+ changed little over a 140-fold difference in chloride concentration. Proton leak rates were faster in CURL and RRC than in MVB, but proton efflux was similar. Finally, proton fluxes and permeabilities, calculated with regard to surface area, differed in the opposite direction (MVB > CURL > RRC). Thus, for the endocytic vesicles studied, intrinsic differences in proton flux and in vesicle geometry could be demonstrated that contributed to differences in pre-steady-state vesicle pHi.