Apical and basolateral pools of proteinase-activated receptor-2 direct distinct signaling events in the intestinal epithelium.
Studies suggest that there are two distinct pools of proteinase-activated receptor-2 (PAR₂) present in intestinal epithelial cells: an apical pool accessible from the lumen, and a basolateral pool accessible from the interstitial space and blood. Although introduction of PAR₂ agonists such as 2-furoyl-LIGRL-O-NH₂ (2fAP) to the intestinal lumen can activate PAR₂, the presence of accessible apical PAR₂ has not been definitively shown. Furthermore, some studies have suggested that basolateral PAR₂ responses in the intestinal epithelium are mediated indirectly by neuropeptides released from enteric nerve fibers, rather than by intestinal PAR₂ itself. Here we identified accessible pools of both apical and basolateral PAR₂ in cultured Caco2-BBe monolayers and in mouse ileum. Activation of basolateral PAR₂ transiently increased short-circuit current by activating electrogenic Cl⁻ secretion, promoted dephosphorylation of the actin filament-severing protein, cofilin, and activated the transcription factor, AP-1, whereas apical PAR₂ did not. In contrast, both pools of PAR₂ activated extracellular signal-regulated kinase 1/2 (ERK1/2) via temporally and mechanistically distinct pathways. Apical PAR₂ promoted a rapid, biphasic PLCβ/Ca²(+)/PKC-dependent ERK1/2 activation, resulting in nuclear localization, whereas basolateral PAR₂ promoted delayed ERK1/2 activation which was predominantly restricted to the cytosol, involving both PLCβ/Ca²(+) and β-arrestin-dependent pathways. These results suggest that the outcome of PAR₂ activation is dependent on the specific receptor pool that is activated, allowing for fine-tuning of the physiological responses to different agonists.
University of California, Riverside, 92521, USA.
Chang
C
Lau
Christian
C
Lytle
Daniel S
DS
Straus
Kathryn A
KA
DeFea
D000818:Animals; D018938:Caco-2 Cells; D002712:Chlorides / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D005260:Female; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D007082:Ileum / Q000502:physiology; D007413:Intestinal Mucosa / Q000166:cytology* / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D044464:Receptor, PAR-2 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
D002712:Chlorides; D044464:Receptor, PAR-2; D048049:Extracellular Signal-Regulated MAP Kinases; D043802:GTP-Binding Protein alpha Subunits, Gq-G11