Maintenance of colonic homeostasis by distinctive apical TLR9 signalling in intestinal epithelial cells.
The mechanisms by which commensal bacteria suppress inflammatory signalling in the gut are still unclear. Here, we present a cellular mechanism whereby the polarity of intestinal epithelial cells (IECs) has a major role in colonic homeostasis. TLR9 activation through apical and basolateral surface domains have distinct transcriptional responses, evident by NF-kappaB activation and cDNA microarray analysis. Whereas basolateral TLR9 signals IkappaBalpha degradation and activation of the NF-kappaB pathway, apical TLR9 stimulation invokes a unique response in which ubiquitinated IkappaB accumulates in the cytoplasm preventing NF-kappaB activation. Furthermore, apical TLR9 stimulation confers intracellular tolerance to subsequent TLR challenges. IECs in TLR9-deficient mice, when compared with wild-type and TLR2-deficient mice, display a lower NF-kappaB activation threshold and these mice are highly susceptible to experimental colitis. Our data provide a case for organ-specific innate immunity in which TLR expression in polarized IECs has uniquely evolved to maintain colonic homeostasis and regulate tolerance and inflammation.
Lee
Jongdae
J
Department of Medicine, University of California, San Diego, La Jolla, CA 92093-0663, USA. j142l33@ucsd.edu
Mo
Ji-Hun
JH
Katakura
Kyoko
K
Alkalay
Irit
I
Rucker
Adam N
AN
Liu
Yu-Tsueng
YT
Lee
Hyun-Ku
HK
Shen
Carol
C
Cojocaru
Gady
G
Shenouda
Steve
S
Kagnoff
Martin
M
Eckmann
Lars
L
Ben-Neriah
Yinon
Y
Raz
Eyal
E
D000818:Animals; D018938:Caco-2 Cells; D016764:Cell Polarity; D002738:Chloroquine / Q000494:pharmacology; D003106:Colon / Q000166:cytology* / Q000187:drug effects / Q000473:pathology; D020895:Enterocytes / Q000166:cytology*; D005786:Gene Expression Regulation / Q000187:drug effects; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D007108:Immune Tolerance / Q000187:drug effects; D008024:Ligands; D051379:Mice; D008810:Mice, Inbred C57BL; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051217:Toll-Like Receptor 9 / Q000737:chemistry / Q000378:metabolism*
D008024:Ligands; D012333:RNA, Messenger; D051217:Toll-Like Receptor 9; D002738:Chloroquine