Functionally distinct pools of actin in secretory cells

Area of Science:

• Cell Biology
• Physiology
• Gastroenterology

Background:

• Gastric acid secretion relies on proton pump (H(+),K(+)-ATPase) vesicle trafficking.
• Actin cytoskeleton dynamics are implicated in regulating parietal cell function.

Purpose of the Study:

• To investigate the role of actin turnover in stimulated gastric parietal cells using latrunculin B (Lat B).
• To differentiate actin pools based on their sensitivity to Lat B and their involvement in parietal cell functions.

Main Methods:

• Utilized latrunculin B (Lat B), an actin monomer-binding agent, on isolated gastric glands and cultured parietal cells.
• Assessed acid accumulation, lamellipodia formation, vacuolar swelling, and actin organization (phalloidin staining) under varying Lat B concentrations.
• Examined the effects of Lat B treatment and subsequent stimulation on parietal cell morphology and function.

Main Results:

• High Lat B concentrations (10-50 µM) disrupted actin organization and inhibited H(+),K(+)-ATPase translocation and vacuolar swelling.
• Low Lat B concentrations (0.1-1 µM) affected lamellipodia but not HK translocation or vacuolar swelling in stimulated cells.
• Resting cells showed minimal effects, but stimulation post-wash reversed Lat B-induced abnormalities, suggesting stimulation enhances Lat B effects on a motile actin pool.

Conclusions:

• Identified two distinct actin pools in parietal cells: a Lat B-sensitive pool for motility and a Lat B-resistant pool (likely microvillar) essential for acid secretion.
• Parietal cell stimulation amplifies Lat B's impact on the motile actin pool, highlighting its dynamic nature during secretion.