TY - JOUR
T1 - A differentiation-dependent splice variant of myosin light chain kinase, MLCK1, regulates epithelial tight junction permeability
AU - Clayburgh, Daniel R.
AU - Rosen, Shari
AU - Witkowski, Edwina D.
AU - Wang, Fengjun
AU - Blair, Stephanie
AU - Dudek, Steven
AU - Garcia, Joe G.N.
AU - Alverdy, John C.
AU - Turner, Jerrold R.
PY - 2004/12/31
Y1 - 2004/12/31
N2 - Activation of Na+-nutrient cotransport leads to increased tight junction permeability in intestinal absorptive (villus) enterocytes. This regulation requires myosin II regulatory light chain (MLC) phosphorylation mediated by MLC kinase (MLCK). We examined the spatio-temporal segregation of MLCK isoform function and expression along the crypt-villus axis and found that long MLCK, which is expressed as two alternatively spliced isoforms, accounts for 97 ± 4% of MLC kinase activity in interphase intestinal epithelial cells. Expression of the MLCK1 isoform is limited to well differentiated enterocytes, both in vitro and in vivo, and this expression correlates closely with development of Na+-nutrient cotransport-dependent tight junction regulation. Consistent with, this role, MLCK1 is localized to the perijunctional actomyosin ring. Furthermore, specific knockdown of MLCK1 using siRNA reduced tight junction permeability in monolayers with active Na +-glucose cotransport, confirming a functional role for MLCK1. These results demonstrate unique physiologically relevant patterns of expression and subcellular localization for long MLCK isoforms and show that MLCK1 is the isoform responsible for tight junction regulation in absorptive enterocytes.
AB - Activation of Na+-nutrient cotransport leads to increased tight junction permeability in intestinal absorptive (villus) enterocytes. This regulation requires myosin II regulatory light chain (MLC) phosphorylation mediated by MLC kinase (MLCK). We examined the spatio-temporal segregation of MLCK isoform function and expression along the crypt-villus axis and found that long MLCK, which is expressed as two alternatively spliced isoforms, accounts for 97 ± 4% of MLC kinase activity in interphase intestinal epithelial cells. Expression of the MLCK1 isoform is limited to well differentiated enterocytes, both in vitro and in vivo, and this expression correlates closely with development of Na+-nutrient cotransport-dependent tight junction regulation. Consistent with, this role, MLCK1 is localized to the perijunctional actomyosin ring. Furthermore, specific knockdown of MLCK1 using siRNA reduced tight junction permeability in monolayers with active Na +-glucose cotransport, confirming a functional role for MLCK1. These results demonstrate unique physiologically relevant patterns of expression and subcellular localization for long MLCK isoforms and show that MLCK1 is the isoform responsible for tight junction regulation in absorptive enterocytes.
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U2 - 10.1074/jbc.M408822200
DO - 10.1074/jbc.M408822200
M3 - Article
C2 - 15507455
AN - SCOPUS:11244320355
SN - 0021-9258
VL - 279
SP - 55506
EP - 55513
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 53
ER -