Stimulation-induced differential redistributions of clathrin and clathrin-coated vesicles in axons compared to soma/dend
- PDF / 2,741,389 Bytes
- 11 Pages / 595.276 x 790.866 pts Page_size
- 37 Downloads / 129 Views
en Access
RESEARCH
Stimulation‑induced differential redistributions of clathrin and clathrin‑coated vesicles in axons compared to soma/dendrites Jung‑Hwa Tao‑Cheng*
Abstract Clathrin-mediated endocytosis plays an important role in the recycling of synaptic vesicle in presynaptic terminals, and in the recycling of transmitter receptors in neuronal soma/dendrites. The present study uses electron microscopy (EM) and immunogold EM to document the different categories of clathrin-coated vesicles (CCV) and pits (CCP) in axons compared to soma/dendrites, and the depolarization-induced redistribution of clathrin in these two polar‑ ized compartments of the neuron. The size of CCVs in presynaptic terminals (~ 40 nm; similar to the size of synaptic vesicles) is considerably smaller than the size of CCVs in soma/dendrites (~ 90 nm). Furthermore, neuronal stimulation induces an increase in the number of CCV/CCP in presynaptic terminals, but a decrease in soma/dendrites. Immu‑ nogold labeling of clathrin revealed that in presynaptic terminals under resting conditions, the majority of clathrin molecules are unassembled and concentrated outside of synaptic vesicle clusters. Upon depolarization with high K +, label for clathrin became scattered among de-clustered synaptic vesicles and moved closer to the presynaptic active zone. In contrast to axons, clathrin-labeled CCVs and CCPs were prominent in soma/dendrites under resting condi‑ tions, and became inconspicuous upon depolarization with high K+. Thus, EM examination suggests that the regula‑ tion and mechanism of clathrin-mediated endocytosis differ between axon and dendrite, and that clathrin redistrib‑ utes differently in these two neuronal compartments upon depolarization. Keywords: Electron microscopy, Clathrin-coated vesicles, Clathrin-coated pits, Endocytosis, Synaptic vesicle, Multivesicular body, Glutamate receptors, Transferrin receptors Introduction Clathrin-mediated endocytosis (CME) is a fundamental process of all mammalian cells that enables internalization of receptors and cargos from the plasma membrane (PM) [1, 2]. Clathrin molecules exist as individual triskelia in the cytoplasm, and are assembled on PM via adaptor and accessary proteins forming a clathrin-coated pit (CCP), which can then be pinched off to become a clathrin-coated vesicle (CCV) in the cytoplasm
*Correspondence: [email protected] NINDS Electron Microscopy Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
[1, 2]. Clathrin eventually sheds from CCV and becomes disassembled in the cytoplasm. In neurons, CME plays an important role in synaptic vesicle (SV) recycling in axon terminals [3, 4], preventing unlimited enlargement of surface membrane area due to exocytosis of SVs during stimulation. On the other hand, in soma/dendrites of neurons, CME is involved in the internalization of transmitter receptors, as well as other receptors and cargos [5, 6]. Notably, CCVs in the brain are smaller in axons than in dendrites, wi
Data Loading...
