Syntaxin 2 and SNAP-23 are required for regulated surfactant secretion.
The secretion of lung surfactant in alveolar type II cells is a complex process involving the fusion of lamellar bodies with the plasma membrane. This process is somewhat different from the exocytosis of hormones and neurotransmitters. For example, it is a relatively slower process, and lamellar bodies are very large vesicles with a diameter of approximately 1 microm. SNARE proteins are the conserved molecular machinery of exocytosis in the majority of secretory cells. However, their involvement in surfactant secretion has not been reported. Here, we showed that syntaxin 2 and SNAP-23 are expressed in alveolar type II cells. Both proteins are associated with the plasma membrane, and to some degree with lamellar bodies. An antisense oligonucleotide complementary to syntaxin 2 decreased its mRNA and protein levels. The same oligonucleotide also inhibited surfactant secretion, independent of secretagogues. A peptide derived from the N-terminus of syntaxin 2 or the C-terminus of SNAP-23 significantly inhibited Ca(2+)- and GTPgammaS-stimulated surfactant secretion from permeabilized type II cells in a dose-dependent manner. Furthermore, introduction of anti-syntaxin 2 or anti-SNAP-23 antibodies into permeabilized type II cells also inhibited surfactant release. Our results suggest that syntaxin 2 and SNAP-23 are required for regulated surfactant secretion.
Abonyo
Barack O
BO
Department of Physiological Sciences, Oklahoma State University, Stillwater, Oklahoma 74078, USA.
Gou
Deming
D
Wang
Pengcheng
P
Narasaraju
Telugu
T
Wang
Zhixi
Z
Liu
Lin
L
D000595:Amino Acid Sequence; D000818:Animals; D000954:Antigens, Surface / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D002352:Carrier Proteins / Q000276:immunology / Q000502:physiology*; D002463:Cell Membrane Permeability / Q000276:immunology / Q000502:physiology; D002478:Cells, Cultured; D007106:Immune Sera / Q000494:pharmacology; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism*; D011663:Pulmonary Surfactants / Q000037:antagonists & inhibitors / Q000378:metabolism*; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D050600:SNARE Proteins; D013347:Subcellular Fractions / Q000378:metabolism; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins
D000954:Antigens, Surface; D002352:Carrier Proteins; D007106:Immune Sera; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D016376:Oligonucleotides, Antisense; D010446:Peptide Fragments; D011663:Pulmonary Surfactants; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D012333:RNA, Messenger; C100493:SNAP23 protein, human; D050600:SNARE Proteins; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins