Chloride influx provokes lamellipodium formation in microglial cells

摘要

Lamellipodium extension and retraction is the driving force for cell migration. Although several studies document that activation of chloride channels are essential in cell migration, little is known about their contribution in lamellipodium formation. To address this question, we characterized chloride channels and transporters by whole cell recording and RT-PCR, respectively, as well as quantified lamellipodium formation in murine primary microglial cells as well as the microglial cell-line, BV-2, using time-lapse microscopy. The repertoire of chloride conducting pathways in BV-2 cells included, swelling- activated chloride channels as well as the KCI cotransporters, KCC1, KCC2, KCC3, and KCC4. Swelling-activated chloride channels were either activated by a hypoosmotic solution or by a high KCI saline, which promotes K+ and Cl- influx instead of efflux by KCCs. Conductance through swelling- activated chloride channels was completely blocked by flufenamic acid (200 mu M), SITS (1mM) and DIOA (10 mu M). By exposing primary microglial cells or BV-2 cells to a high KCI saline, we observed a local swelling, which developed into a prominent lamellipodium. Blockade of chloride influx by flufenamic acid (200 mu M) or DIOA (10 mu M) as well as incubation of cells in a chloride-free high K+ saline suppressed formation of a lamellipodium. We assume that local swellings, established by an increase in chloride influx, are a general principle in formation of lamellipodia in eukaryotic cells. Copyright (c) 2008 S. Karger AG, Basel.