Regulation of surfactant secretion

• Published in: Comparative Biochemistry and Physiology, Part A Vol. 129; no. 1; pp. 233 - 243
• Main Author: Rooney, Seamus A
• Format: Book Review Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.2001
• Subjects: Animals; Base Sequence; DNA Primers; Lung surfactant; P2Y 2 receptor; Phospholipase C-β3; Phospholipase D; Protein kinase; Pulmonary Surfactants - secretion; Secretion; Signal Transduction; Type II pneumocyte; Signal transduction; Type II pneumocyte; Secretion; Protein kinase; P2Y 2 receptor; Phospholipase C-β3; Lung surfactant; Phospholipase D
• ISSN: 1095-6433; 1531-4332
• DOI: 10.1016/S1095-6433(01)00320-8

Lung surfactant is synthesized in the alveolar type II cell. Its lipids and hydrophobic proteins (SP-B and SP-C) are stored in lamellar bodies and secreted by regulated exocytosis. In contrast, the hydrophilic proteins (SP-A and SP-D) appear to be secreted independently of lamellar bodies. Regulation of surfactant secretion is mediated by at least three distinct signaling mechanisms: activation of adenylate cyclase with formation of cAMP and activation of cAMP-dependent protein kinase; activation of protein kinase C; and a Ca 2+-regulated mechanism that likely results in the activation of Ca 2+-calmodulin-dependent protein kinase. These signaling mechanisms are activated by a variety of agonists, some of which may have a physiological role. ATP is one such agent and it activates all three signaling mechanisms. There is increasing information on the identity of several of the signaling proteins involved in surfactant secretion although others remain to be established. In particular the identity of the phospholipase C, protein kinase C and phospholipase D isomers expressed in the type II cell and/or involved in surfactant secretion has been established. Distal steps in the secretory pathway beyond protein kinase activation as well as the physiological regulation of surfactant secretion, are major issues that need to be addressed.