Role of MARCKS in regulated secretion from mast cells and airway goblet cells.
MARCKS (myristoylated alanine-rich C kinase substrate) is postulated to regulate the passage of secretory granules through cortical actin in the early phase of exocytosis. There are, however, three proposed mechanisms of action, all of which were derived from studies using synthetic peptides representing either the central phosphorylation site domain or the upstream, NH2-terminal domain: it tethers actin to the plasma membrane and/or to secretory granules, and/or it sequesters PIP2. Using MARCKS-null mice, we probed for a loss of function secretory phenotype in mast cells harvested from embryonic livers and maturated in vivo [embryonic hepatic-derived mast cells (eHMCs)]. Both wild-type (WT) and MARCKS-null eHMCs exhibited full exocytic responses upon FcϵRI receptor activation with DNP-BSA (2,4-dinitrophenyl-BSA), whether they were in suspension or adherent. The secretory responses of MARCKS-null eHMCs were consistently higher than those of WT cells, but the differences had sporadic statistical significance. The MARCKS-null cells exhibited faster secretory kinetics, however, achieving the plateau phase of the response with a t½ ∼2.5-fold faster. Hence, MARCKS appears to be a nonessential regulatory protein in mast cell exocytosis but exerts a negative modulation. Surprisingly, the MARCKS NH2-terminal peptide, MANS, which has been reported to inhibit mucin secretion from airway goblet cells (Li Y, Martin LD, Spizz G, Adler KB. J Biol Chem 276: 40982-40990, 2001), inhibited hexosaminidase secretion from WT and MARCKS-null eHMCs, leading us to reexamine its effects on mucin secretion. Results from studies using peptide inhibitors with human bronchial epithelial cells and with binding assays using purified mucins suggested that MANS inhibited the mucin binding assay, rather than the secretory response.
Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina and Department of Cell and Molecular Physiology, University of North Carolina, Chapel Hill, North Carolina.
Brookelyn J
BJ
Haddock
Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina and.
Yunxiang
Y
Zhu
Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina and.
Sean P
SP
Doyle
Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina and.
Lubna H
LH
Abdullah
Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina and Department of Cell and Molecular Physiology, University of North Carolina, Chapel Hill, North Carolina cwdavis@med.unc.edu.
C William
CW
Davis
D000818:Animals; D001980:Bronchi / Q000166:cytology; D002478:Cells, Cultured; D005089:Exocytosis; D020397:Goblet Cells / Q000378:metabolism*; D006596:Hexosaminidases / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology*; D007700:Kinetics; D008407:Mast Cells / Q000378:metabolism*; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009077:Mucins / Q000378:metabolism*; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D010446:Peptide Fragments / Q000502:physiology
D047908:Intracellular Signaling Peptides and Proteins; C000619710:MARCKS protein, human; C000619711:Marcks protein, mouse; D008565:Membrane Proteins; D009077:Mucins; D010446:Peptide Fragments; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D006596:Hexosaminidases
MANS peptide; MARCKS; airway goblet cells; exocytosis; mast cells; mucin secretion