Regulation of M2-type pyruvate kinase mediated by the high-affinity IgE receptors is required for mast cell degranulation.
OBJECTIVE
M2-type pyruvate kinase (M2PK) was found to interact directly with the 'ITAM' region of the gamma chain of the high-affinity IgE receptor (FcvarepsilonRI). Our hypothesis was that mast cell degranulation might require the FcvarepsilonRI-mediated inhibition of M2PK activity.


METHODS
In rat basophilic leukaemia (RBL-2H3) cells, the effects of directly inhibiting M2PK or preventing the FcvarepsilonRI-mediated inhibition of M2PK (disinhibition) on degranulation was measured by hexosaminidase release. Effects of blocking the FcvarepsilonRI-mediated inhibition of M2PK was also assessed in vivo in a mouse model of allergen-induced airway hyper-responsiveness.


RESULTS
Activation of FcvarepsilonRI in RBL-2H3 cells caused the rapid phosphorylation of tyrosine residues in M2PK, associated with a decrease in M2PK enzymatic activity. There was an inverse correlation between M2PK activity and mast cell degranulation. FcvarepsilonRI-mediated inhibition of M2PK involved Src kinase, phosphatidylinositol 3-kinase, PKC and calcium. Direct inhibition of M2PK potentiated FcvarepsilonRI-mediated degranulation and prevention of the FcvarepsilonRI-mediated inhibition of M2PK attenuated mast cell degranulation. Transfection of RBL-2H3 cells with M1PK which prevents FcvarepsilonRI-induced inhibition of M2PK, markedly reduced their degranulation and exogenous M1PK (i.p.) inhibited ovalbumin-induced airway hyper-responsiveness in vivo.


CONCLUSIONS
We have identified a new control point and a novel biochemical pathway in the process of mast cell degranulation. Our study suggests that the FcvarepsilonRI-mediated inhibition of M2PK is a crucial step in responses to allergens. Moreover, the manipulation of glycolytic processes and intermediates could provide novel strategies for the treatment of allergic diseases.
Ryu
H
H
Department of Pharmacology, Research Institute of Drug Development, College of Pharmacy, Chonnam National University, Kwang-Ju, Korea.
Walker
J K L
JK
Kim
S
S
Koo
N
N
Barak
L S
LS
Noguchi
T
T
Kang
B Y
BY
Kim
K-M
KM
D000818:Animals; D016535:Bronchial Hyperreactivity / Q000201:enzymology / Q000276:immunology / Q000517:prevention & control; D002118:Calcium / Q000378:metabolism; D015550:Cell Degranulation / Q000187:drug effects; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006019:Glycolysis; D006596:Hexosaminidases / Q000378:metabolism; D008297:Male; D008407:Mast Cells / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D010047:Ovalbumin; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011770:Pyruvate Kinase / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017455:Receptors, IgE / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection; D019061:src-Family Kinases / Q000378:metabolism
D004791:Enzyme Inhibitors; D017455:Receptors, IgE; D010047:Ovalbumin; D019869:Phosphatidylinositol 3-Kinases; D011770:Pyruvate Kinase; D019061:src-Family Kinases; D011493:Protein Kinase C; D006596:Hexosaminidases; D002118:Calcium