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J. Biol. Chem., Vol. 277, Issue 5, 3793-3800, February 1, 2002
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From the Departments of Paneth cells in small intestinal crypts secrete
microbicidal
Modulation of Mouse Paneth Cell
-Defensin Secretion by mIKCa1,
a Ca2+-activated, Intermediate Conductance Potassium
Channel*
,
, and
**
Pathology,
§ Physiology and Biophysics, and
Microbiology and
Molecular Genetics, College of Medicine, University of California,
Irvine, California 92697-4800 and the ¶ INSERM U 410, Faculté de Médecine Xavier Bichat,
75018 Paris, France
-defensins in response to bacteria and bacterial
antigens (Ayabe, T., Satchell, D. P., Wilson, C. L., Parks,
W. C., Selsted, M. E., and Ouellette, A. J. (2000)
Nat. Immunol. 1, 113-138). We now report that the
Ca2+-activated K+ channel mIKCa1 modulates
mouse Paneth cell secretion. mIKCa1 cDNA clones identified in a
mouse small intestinal crypt library by hybridization to human IKCa1
cDNA probes were isolated, and DNA sequence analysis showed that
they were identical to mIKCa1 cDNAs isolated from erythroid cells
and liver. The genomic organization was found to be conserved between
mouse and human IKCa1 as shown by comparisons of the respective
cDNA and genomic sequences. Reverse transcriptase-PCR experiments
using nested primers amplified mIKCa1 from the lower half of bisected
crypts and from single Paneth cells, but not from the upper half of
bisected crypts, villus epithelium, or undifferentiated crypt
epithelial cells, suggesting a lineage-specific role for mIKCa1 in
mouse small bowel epithelium. The cloned mIKCa1 channel was
calcium-activated and was blocked by ten structurally diverse peptide
and nonpeptide inhibitors with potencies spanning 9 orders of magnitude
and indistinguishable from that of the human homologue. Consistent with
channel blockade, charybdotoxin, clotrimazole, and the highly selective
IKCa1 inhibitors, TRAM-34 and TRAM-39, inhibited (~50%) Paneth cell
secretion stimulated by bacteria or bacterial lipopolysaccharide,
measured both as bactericidal activity and secreted cryptdin protein,
but the inactive analog, TRAM-7, did not block secretion. These results
demonstrate that mIKCa1 is modulator of Paneth cell
-defensin
secretion and disclose an involvement in mucosal defense of the
intestinal epithelium against ingested bacterial pathogens.
*
This work was supported by National Institutes of Health
Grants DK44632 (to A. J. O), MH59222 (to K. G. C.), and
NS14609 (to M. D. C.) and by Western States Affiliate of the
American Heart Association Award 9920014Y (to H. W.).The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
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