Zheng Ning, Jeyifous Okunola, Munro Charlotte, Montgomery Johanna M, Green William N
Department of Neurobiology, University of Chicago, Chicago, United States.
Department of Physiology, University of Auckland, Auckland, New Zealand.
Elife. 2015 May 13;4:e06878. doi: 10.7554/eLife.06878.
Changes in glutamatergic synaptic strength in brain are dependent on AMPA-type glutamate receptor (AMPAR) recycling, which is assumed to occur through a single local pathway. In this study, we present evidence that AMPAR recycling occurs through different pathways regulated by synaptic activity. Without synaptic stimulation, most AMPARs recycled in dynamin-independent endosomes containing the GTPase, Arf6. Few AMPARs recycled in dynamin-dependent endosomes labeled by transferrin receptors (TfRs). AMPAR recycling was blocked by alterations in the GTPase, TC10, which co-localized with Arf6 endosomes. TC10 mutants that reduced AMPAR recycling had no effect on increased AMPAR levels with long-term potentiation (LTP) and little effect on decreased AMPAR levels with long-term depression. However, internalized AMPAR levels in TfR-containing recycling endosomes increased after LTP, indicating increased AMPAR recycling through the dynamin-dependent pathway with synaptic plasticity. LTP-induced AMPAR endocytosis is inconsistent with local recycling as a source of increased surface receptors, suggesting AMPARs are trafficked from other sites.
大脑中谷氨酸能突触强度的变化取决于AMPA型谷氨酸受体(AMPAR)的循环利用,一般认为其通过单一局部途径发生。在本研究中,我们提供证据表明AMPAR循环利用通过受突触活动调节的不同途径发生。在没有突触刺激的情况下,大多数AMPAR在含有GTP酶Arf6的发动蛋白非依赖性内体中循环利用。少数AMPAR在由转铁蛋白受体(TfRs)标记的发动蛋白依赖性内体中循环利用。AMPAR循环利用被与Arf6内体共定位的GTP酶TC10的改变所阻断。降低AMPAR循环利用的TC10突变体对长期增强(LTP)导致的AMPAR水平升高没有影响,对长期抑制导致的AMPAR水平降低影响也很小。然而,LTP后含TfR的循环内体中内化的AMPAR水平增加,表明随着突触可塑性,通过发动蛋白依赖性途径的AMPAR循环利用增加。LTP诱导的AMPAR内吞作用与作为表面受体增加来源的局部循环利用不一致,这表明AMPAR是从其他部位转运而来的。