Occludin phosphorylation: identification of an occludin kinase in brain and cell extracts as CK2.
In epithelial and endothelial cells, tight junctions limit paracellular flux of ions, proteins and other macromolecules. However, mechanisms regulating tight junction function are not clear. Occludin, a tight junction protein, undergoes phosphorylation changes in several situations but little is known about occludin kinases. A recombinant C-terminal fragment of occludin is a substrate for a kinase in crude extracts of brain. This activity was purified about 10000-fold and identified as CK2 (casein kinase 2) by peptide mass fingerprinting, immunoblotting and mutation of CK2 sites within the occludin sequence. CK2 is therefore a candidate kinase for regulation of occludin phosphorylation in vivo.
Smales
Caroline
C
Eisai London Research Laboratories Ltd., Bernard Katz Building, University College London, Gower Street, London, WC1E 6BT, UK.
Ellis
Moira
M
Baumber
Rachel
R
Hussain
Nayer
N
Desmond
Howard
H
Staddon
James M
JM
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000201:enzymology*; D047390:Casein Kinase II; D002457:Cell Extracts / Q000737:chemistry*; D002458:Cell Fractionation; D008565:Membrane Proteins / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D062793:Occludin; D010766:Phosphorylation; D017354:Point Mutation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013552:Swine
D002457:Cell Extracts; D008565:Membrane Proteins; D062793:Occludin; D011994:Recombinant Proteins; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases