Meeting Abstract
Phosphatidylserine is important for clathrin-mediated endocytosis Author Block: *K.Varga, L-W. Gong; Department of Biological Sciences, Laboratory of Integrative Neuroscience, UIC, Chicago, IL Phosphatidylserine (PS) is the most abundant negatively charged phospholipid species found within eukaryotic membranes. Its biological importance is displayed through its unique biochemical properties, most notably through its direct binding to proteins bearing C2 domains. Interestingly, PS is highly relevant to vesicle exocytosis at synapses via its interaction with vesicular protein Synaptotagmin 1 (syt 1) C2 domains. Concurrently, endocytosis occurs at synapses to maintain synaptic integrity. However, it remains unclear whether PS plays a role during synaptic vesicle endocytosis. In the present study, clathrin-mediated endocytosis (CME) of single vesicles was monitored using cell-attached capacitance measurements in the mouse adrenal chromaffin cell. In this approach, a sinusoidal voltage is superimposed to the holding potential and a two-phase lock-in amplifier is used to analyze the current output signal. From here, the two outputs of the amplifier provide direct changes of both membrane conductance and membrane capacitance. Supplementation of PS, was compared to supplementation of two other neutrally charged lipid species: phosphatidylethylalomine (PE) or phosphatidylcholine (PC). These additions were carried out in chromaffin cells in culture prior to cell-attached electrophysiology. Our results showed that: (1) Negatively charged PS but not neutrally charged PC or PE, significantly decreased the fission-pore duration during the last stage of vesicle retrieval; and (2) the Ca2+ dependence of CME kinetics was shifted by PS addition.
