Increased Vesicle Recycling in Response to Osmotic Cell Swelling

Abstract

Osmotic swelling of Intestine 407 cells leads to an immediate increase in cell surface membrane area as determined using the fluorescent membrane dye FM 1-43. In addition, as measured by tetramethylrhodamine isothiocyanate (TRITC)-dextran uptake, a robust (>100-fold) increase in the rate of endocytosis was observed, starting after a discrete lag time of 2-3 min and lasting for ϳ10 In mammalian cells, hypotonic cell swelling leads to the activation of cell volume regulatory processes, which in general involves a transient increase in the K ϩ and Cl Ϫ conductances (for reviews see Refs. 1-3). As a result, KCl leaves the cell, and cellular volume is rapidly restored (regulatory volume decrease). In addition to ion channel activation, osmotic swelling, like many other forms of mechanical stress, is known to promote the release of ATP, a potentially auto-or paracrinic factor acting through plasma membrane purinoceptors (4 -7). Extracellular ATP has been shown to regulate to the regulatory volume decrease response in a number of different cell types (4,5,8,9), either through the stimulation of a Ca 2ϩ -dependent K ϩ efflux (8) or by the activation of the volume-sensitive Cl Ϫ channels (4, 9). In Intestine 407 cells, extracellular ATP is not required for the direct activation of volume-sensitive Cl Ϫ channels (7). However, (sub)micromolar concentrations of extracellular ATP were able to potentiate the hypotonicity-provoked Cl Ϫ efflux in a Ca 2ϩ -dependent manner (7). In addition, osmotically induced ATP release was found to be critically involved in the activation of extracellular signal-regulated protein kinase (Erk) 1 -1/2 in Intestine 407 cells (7). Although the role of Erk-1/2 activation in the regulatory volume decrease response remains to be elucidated, activation of these MAP kinases by cell swelling has been observed in all cell models studied so far (10 -20).To date, several potential mechanisms have been proposed to explain cellular release of ATP. These include the following: 1) leakage due to (local) membrane damage; 2) activation of specific channel(s) or transporter(s); and 3) exocytotic events. Previously, members of the ABC-superfamily of transporters were suggested to permeate ATP (for reviews see Refs. 21 and 22). Intestine 407 cells, however, lack CFTR expression, and in the subclone we use, P-glycoprotein expression was not detected (7, 10) arguing against a role for ABC transporters in the ATP release. Because the cell swelling-induced ATP release differs from the activation of osmo-sensitive Cl Ϫ channels in both the time scale of activation/inactivation and in its sensitivity to inhibitors (6, 7), it was concluded that ATP does not permeate through volume-sensitive anion channels. In contrast, in Intestine 407 cells, the ATP release was found to depend largely on [Ca 2ϩ ] i as well as on an intact cytoskeleton (7). In this study, we pursued the hypothesis that regulated exocytosis might be involved in the release of ATP. In a number of cell models it was found that disruption of soluble N-ethy...

Myosin light chain kinase and Src control membrane dynamics in volume recovery from cell swelling

“…By contrast, osmotic cell swelling (e.g., produced by hypotonic challenge) is associated with a marked increase in membrane turnover (van der Wijk et al , 2003). The time period of volume-sensitive exocytosis in liver cells (Feranchak et al , 2010) overlaps with the time period of blebbing that we have observed under similar conditions of hypotonic exposure (Barfod et al , 2005), suggesting that bleb expansion during osmotic stress could include contributions of membrane from within the cell.…”

“…In a number of cell types, hypotonic challenge evokes exocytosis (Straub et al , 2002; Gatof et al , 2004; Musch et al , 2004), which peaks during the time of cell swelling; this is followed by endocytic membrane retrieval during the time of volume recovery (van der Wijk et al , 2003). Compensatory endocytosis has been observed in response to a variety of stimulated secretory processes (Sokac and Bement, 2006).…”

Physiological Regulation of ATP Release at the Apical Surface of Human Airway Epithelia

“…Non-lytic mechanisms for hypotonicity-induced ATP release may include regulated exocytosis and/or conductive/transporter pathways (41,55,56). The driving force for ATP release onto the surface of HBE cells via conductive pathways is large, i.e.…”

Barriers to inhaled gene therapy of obstructive lung diseases: A review

“…During this endocytic process, particulates, including inhaled gene vectors, in the vicinity of the apical membrane can be taken up by epithelial cells. The RVD effect has been shown to last up to 30 minutes [317, 319]. Potential safety concern resulting from hypotonic shock would need to be addressed before clinical implementation of this approach.…”