AMP-activated protein kinase regulates the assembly of epithelial tight junctions

doi:10.1073/pnas.0608531103

AMP-activated protein kinase regulates the assembly of epithelial tight junctions

*Department of Cell Biology,
^†Department of Internal Medicine, Section of Cardiovascular Medicine, and
^‡Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520

Communicated by Joseph F. Hoffman, Yale University School of Medicine, New Haven, CT, September 27, 2006 (received for review June 9, 2006)

Abstract

AMP activated protein kinase (AMPK), a sensor of cellular energy status in all eukaryotic cells, is activated by LKB1-dependent phosphorylation. Recent studies indicate that activated LKB1 induces polarity in epithelial cells and that this polarization is accompanied by the formation of tight junction structures. We wished to determine whether AMPK also contributes to the assembly of tight junctions in the epithelial cell polarization process. We found that AMPK is activated during calcium-induced tight junction assembly. Activation of AMPK by 5-aminoimidazole-4-carboxamide ribonucleoside facilitates tight junction assembly under conditions of normal extracellular Ca²⁺ concentrations and initiates tight junction assembly in the absence of Ca²⁺ as revealed by the relocation of zonula occludens 1, the establishment of transepithelial electrical resistance, and the paracellular flux assay. Expression of a dominant negative AMPK construct inhibits tight junction assembly in MDCK cells, and this defect in tight junction assembly can be partially ameliorated by rapamycin. These results suggest that AMPK plays a role in the regulation of tight junction assembly.

AMPK
ZO-1

Footnotes

^§To whom correspondence should be addressed at:
Department of Cellular and Molecular Physiology, Yale University School of Medicine, P.O. Box 208026, New Haven, CT 06520-8026.
E-mail: michael.caplan{at}yale.edu
Author contributions: L.Z., L.H.Y., and M.J.C. designed research; L.Z. and J.L. performed research; J.L. contributed new reagents/analytic tools; L.Z., L.H.Y., and M.J.C. analyzed data; and L.Z. and M.J.C. wrote the paper.
The authors declare no conflict of interest.
Abbreviations:

2-DG,

2-deoxy-d-glucose;

ACC,

acetyl coenzyme A carboxylase;

AICAR,

5-aminoimidazole-4-carboxamide ribonucleoside;

AMPK,

AMP-activated protein kinase;

CaMKK,

calcium/calmodulin-dependent protein kinase kinase;

DN,

dominant negative;

HCM,

high-calcium medium;

LCM,

low-calcium medium;

MARK,

microtubule-affinity-regulating kinases;

mTOR,

mammalian target of rapamycin;

PAR,

partitioning-defect;

TER,

transepithelial electrical resistance;

TSC,

tuberous sclerosis complex;

ZO-1,

zonula occludens 1.