ATP is stored in lamellar bodies to activate vesicular P2X in an autocrine fashion upon exocytosis.

Vesicular P2X receptors are known to facilitate secretion and activation of pulmonary surfactant in the alveoli of the lungs. P2X receptors are expressed in the membrane of lamellar bodies (LBs), large secretory lysosomes that store lung surfactant in alveolar type II epithelial cells, and become inserted into the plasma membrane after exocytosis. Subsequent activation of P2X receptors by adenosine triphosphate (ATP) results in local fusion-activated cation entry (FACE), facilitating fusion pore dilation, surfactant secretion, and surfactant activation.

Local detection of mechanically induced ATP release from bone cells with ATP microbiosensors.

The mechanically induced release of adenosine-5'-triphosphate (ATP) from osteoblastic cells (MC3T3-E1) was measured in real time. A stretching device integrated into scanning electrochemical microscopy was developed to apply controlled mechanical strain to MC3T3-E1 cells. For ATP secretion, a stepwise yet uniform mechanical stress was imposed onto MC3T3-E1 cells.

Fusion-activated cation entry (FACE) via P2X₄ couples surfactant secretion and alveolar fluid transport.

Two fundamental mechanisms within alveoli are essential for lung function: regulated fluid transport and secretion of surfactant. Surfactant is secreted via exocytosis of lamellar bodies (LBs) in alveolar type II (ATII) cells. We recently reported that LB exocytosis results in fusion-activated cation entry (FACE) via P2X₄ receptors on LBs.

Combined atomic force microscopy-fluorescence microscopy: analyzing exocytosis in alveolar type II cells.

Hybrid atomic force microscopy (AFM)-fluorescence microscopy (FM) investigation of exocytosis in lung epithelial cells (ATII cells) allows the detection of individual exocytic events by FM, which can be simultaneously correlated to structural changes in individual cells by AFM. Exocytosis of lamellar bodies (LBs) represents a slow form of exocytosis found in many non-neuronal cells. Exocytosis of LBs, following stimulation with adenosine-5'-triphosphate (ATP) and phorbol 12-myristate 13-acetate (PMA), results in a cation influx via P2X(4) receptors at the site of LB fusion with the plasma membrane (PM), which should induce a temporary increase in cell height/volume.

Actin coating and compression of fused secretory vesicles are essential for surfactant secretion--a role for Rho, formins and myosin II.

Secretion of vesicular contents by exocytosis is a fundamental cellular process. Increasing evidence suggests that post-fusion events play an important role in determining the composition and quantity of the secretory output. In particular, regulation of fusion pore dilation and closure is considered a key regulator of the post-fusion phase.

Atomic force microscopy of microvillous cell surface dynamics at fixed and living alveolar type II cells.

Scanning probe techniques enable direct imaging of morphology changes associated with cellular processes at life specimen. Here, glutaraldehyde-fixed and living alveolar type II (ATII) cells were investigated by atomic force microscopy (AFM), and the obtained topographical data were correlated with results obtained by scanning electron microscopy (SEM) and confocal microscopy (CM). We show that low-force contact mode AFM at glutaraldehyde-fixed cells provides complementary results to SEM and CM.