Regulation of riboflavin intestinal uptake by protein kinase A

Studies with Caco-2 cells

H. M. Said, Thomas Ma, K. Grant

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Although the mechanism of riboflavin (RF) intestinal uptake has been the subject of many studies, virtually nothing is known about the cellular regulation of the uptake process. In the present study, we investigated the role of protein kinase A (PKA)- and C (PKC)-mediated pathways in the regulation of RF intestinal uptake using the confluent Caco-2 monolayers. Treatment of Caco-2 cells with 3-isobutyl-1-methylxanthine (IBMX), forskolin, cholera toxin, or dibutyryl adenosine 3',5'-cyclic monophosphate caused a significant inhibition in RF uptake. The inhibitory effect of IBMX was reversible and resulted from a significant decrease in the maximal velocity of the RF uptake process with no change in its apparent Michaelis constant. The IBMX-induced inhibition in RF uptake was not mediated via inhibition in the synthesis of the RF carrier protein or through inhibition in the recruitment of preexisting carrier protein into the plasma membrane. Calyculin A also inhibited RF uptake when added alone and further potentiated the inhibitory effect of IBMX when added together. Phorbol 12-myristate 13- acetate or chelerythrine, on the other hand, showed no significant effect on RF uptake. These results demonstrate for the first time that compounds that increase intracellular cAMP levels downregulate RF intestinal uptake and that this effect is mediated via a decrease in the activity of the RF uptake carrier. It is suggested that a PKA-mediated pathway(s) plays an important role in regulating RF intestinal uptake.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume267
Issue number6 30-6
StatePublished - Dec 1 1994

Fingerprint

Caco-2 Cells
Riboflavin
Cyclic AMP-Dependent Protein Kinases
1-Methyl-3-isobutylxanthine
Bucladesine
Cholera Toxin
Colforsin
Protein Kinase C
Carrier Proteins
Acetates
Down-Regulation
Cell Membrane

All Science Journal Classification (ASJC) codes

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)

Cite this

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title = "Regulation of riboflavin intestinal uptake by protein kinase A: Studies with Caco-2 cells",
abstract = "Although the mechanism of riboflavin (RF) intestinal uptake has been the subject of many studies, virtually nothing is known about the cellular regulation of the uptake process. In the present study, we investigated the role of protein kinase A (PKA)- and C (PKC)-mediated pathways in the regulation of RF intestinal uptake using the confluent Caco-2 monolayers. Treatment of Caco-2 cells with 3-isobutyl-1-methylxanthine (IBMX), forskolin, cholera toxin, or dibutyryl adenosine 3',5'-cyclic monophosphate caused a significant inhibition in RF uptake. The inhibitory effect of IBMX was reversible and resulted from a significant decrease in the maximal velocity of the RF uptake process with no change in its apparent Michaelis constant. The IBMX-induced inhibition in RF uptake was not mediated via inhibition in the synthesis of the RF carrier protein or through inhibition in the recruitment of preexisting carrier protein into the plasma membrane. Calyculin A also inhibited RF uptake when added alone and further potentiated the inhibitory effect of IBMX when added together. Phorbol 12-myristate 13- acetate or chelerythrine, on the other hand, showed no significant effect on RF uptake. These results demonstrate for the first time that compounds that increase intracellular cAMP levels downregulate RF intestinal uptake and that this effect is mediated via a decrease in the activity of the RF uptake carrier. It is suggested that a PKA-mediated pathway(s) plays an important role in regulating RF intestinal uptake.",
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Regulation of riboflavin intestinal uptake by protein kinase A : Studies with Caco-2 cells. / Said, H. M.; Ma, Thomas; Grant, K.

In: American Journal of Physiology - Gastrointestinal and Liver Physiology, Vol. 267, No. 6 30-6, 01.12.1994.

Research output: Contribution to journalArticle

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