David Foley - An energy supply network of nutrient absorption coordinated by calcium and T1R taste receptors in rat small intestine

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      Publication Details (including relevant citation   information):

      O. J. Mace, N. Lister, E. Morgan, E. Shepherd, J. Affleck, P.   Helliwell, J. R. Bronk, G. L. Kellett, D. Meredith, R. Boyd, M.   Pieri, P. D. Bailey, R. Pettecrew and D. Foley


      J. Physiol. (2009),   587,   195-210.


      DOI: 10.1113/jphysiol.2008.159616


      T1R taste receptors are present throughout the gastrointestinal   tract. Glucose absorption comprises active absorption via SGLT1   and facilitated absorption via GLUT2 in the apical membrane.   Trafficking of apical GLUT2 is rapidly up-regulated by glucose   and artificial sweeteners, which act through T1R2 +   T1R3/α-gustducin to activate PLC β2 and PKC βII. We therefore   investigated whether non-sugar nutrients are regulated by taste   receptors using perfused rat jejunum in vivo. Under   different conditions, we observed a Ca2+-dependent   reciprocal relationship between the H+/oligopeptide   transporter PepT1 and apical GLUT2, reflecting the fact that   trafficking of PepT1 and GLUT2 to the apical membrane is   inhibited and activated by PKC βII, respectively. Addition of   l-glutamate or sucralose to a perfusate containing low glucose   (20 mm) each activated PKC βII and decreased apical PepT1 levels   and absorption of the hydrolysis-resistant dipeptide   l-Phe(ΨS)-l-Ala (1 mm), while increasing apical GLUT2 and glucose   absorption within minutes. Switching perfusion from mannitol to   glucose (75 mm) exerted similar effects. l-Glutamate induced   rapid GPCR internalization of T1R1, T1R3 and transducin, whereas   sucralose internalized T1R2, T1R3 and α-gustducin. We conclude   that l-glutamate acts via amino acid and glucose via sweet taste   receptors to coordinate regulation of PepT1 and apical GLUT2   reciprocally through a common enterocytic pool of PKC βII. These   data suggest the existence of a wider Ca2+ and taste   receptor-coordinated transport network incorporating other   nutrients and/or other stimuli capable of activating PKC βII and   additional transporters, such as the aspartate/glutamate   transporter, EAAC1, whose level was doubled by l-glutamate. The   network may control energy supply.

      Address (URL): http://jp.physoc.org/content/587/1/195.abstract