Osteoclast spreading kinetics are correlated with an oscillatory activation of a calcium-dependent potassium current

Abstract

Cell movement and spreading involve calcium-dependent processes and ionic channel activation. During bone resorption, osteoclasts alternate between spread, motile and resorptive phases. We investigated whether the electrical membrane properties of osteoclasts were linked to their membrane morphological changes. Rabbit osteoclasts were recorded by time-lapse videomicroscopy performed simultaneously with patch-clamp whole cell and single channel recordings. Original image analysis methods were developed and used to demonstrate for the first time an oscillatory activation of a spontaneous membrane current in osteoclasts, which is directly correlated to the membrane movement rate. This current was identified as a calcium-dependent potassium current (IKCa) that is sensitive to both charybdotoxin and apamin and was generated by a channel with unitary conductance of approximately 25±2 pS. Blockade of this current also decreased osteoclast spreading and inhibited bone resorption in vitro, demonstrating a physiological role for this current in osteoclast activity. These results establish for the first time a temporal correlation between lamellipodia formation kinetics and spontaneous peaks of IKCa, which are both involved in the control of osteoclast spreading and bone resorption.

Cells move when ions and water flow

“…Accordingly, activation of IK1 channels results in a localized shrinkage of migrating cells at their trailing edge, thereby supporting the retraction of this cell pole [114]. In osteoclasts, IK1 channels are also involved in cell spreading [26] (Fig. 1).…”

Evidence for Mitoxantrone-induced Block of Inwardly Rectifying K+Channels Expressed in the Osteoclast Precursor RAW 264.7 Cells Differentiated with Lipopolysaccharide

“…The Kir channel activity was not functionally expressed in MG-63 osteoblast-like cells; however, we did �ind the presence of Kir channels in BV-2 microglial cells (data not shown). Therefore, in LPS-treated RAW 264.7 cells, MX-mediated inhibition of I K(IR) can result in membrane depolarization, which decreases in the inwardly directed driving force for Ca 2+ and subsequently diminishes the amplitude of Ca 2+ -activated K + currents [17]. It is anticipated that such positive feedback of membrane depolarization on Kir channels in LPS-treated RAW 264.7 cells is unique and provides an ideal tool for �ine tuning of Kir-channel activity.…”

“…Specially, because RAW 264.7 cells act as osteoclast progenitors and can differentiate into osteoclasts in response to either lipopolysaccharide (LPS) or receptor activator of nuclear factor κB ligand [10,[12][13][14][15], they have attracted growing interest as a suitable model for studies of functional activities in osteoclasts. Several reports have described the electrical properties of these cells [3,11,[16][17][18][19][20]. To our knowledge, how MX and other structurally related compounds interact with ion currents in these cells is still not fully understood.…”

Characterisation of Mytilus edulis hemocyte subpopulations by single cell time-lapse motility imaging

“…The main goal was to quantify membrane deformations during cell displacements by monitoring expansions of the membrane margin with respect to the cell centroid, as already done in rabbit osteoclasts [33] and in mouse embryonic fibroblasts [34]. Briefly, the method proceeds as follow (see Fig.…”