Fc{epsilon}RI-mediated mast cell degranulation requires calcium-independent microtubule-dependent translocation of granules to the plasma membrane.
The aggregation of high affinity IgE receptors (Fcepsilon receptor I [FcepsilonRI]) on mast cells is potent stimulus for the release of inflammatory and allergic mediators from cytoplasmic granules. However, the molecular mechanism of degranulation has not yet been established. It is still unclear how FcepsilonRI-mediated signal transduction ultimately regulates the reorganization of the cytoskeleton and how these events lead to degranulation. Here, we show that FcepsilonRI stimulation triggers the formation of microtubules in a manner independent of calcium. Drugs affecting microtubule dynamics effectively suppressed the FcepsilonRI-mediated translocation of granules to the plasma membrane and degranulation. Furthermore, the translocation of granules to the plasma membrane occurred in a calcium-independent manner, but the release of mediators and granule-plasma membrane fusion were completely dependent on calcium. Thus, the degranulation process can be dissected into two events: the calcium-independent microtubule-dependent translocation of granules to the plasma membrane and calcium-dependent membrane fusion and exocytosis. Finally, we show that the Fyn/Gab2/RhoA (but not Lyn/SLP-76) signaling pathway plays a critical role in the calcium-independent microtubule-dependent pathway.
Laboratory for Cytokine Signaling, RIKEN Research Center for Allergy and Immunology, Kanagawa 230-0045, Japan.
Keigo
K
Nishida
Satoru
S
Yamasaki
Yukitaka
Y
Ito
Koki
K
Kabu
Kotaro
K
Hattori
Tohru
T
Tezuka
Hirofumi
H
Nishizumi
Daisuke
D
Kitamura
Ryo
R
Goitsuka
Raif S
RS
Geha
Tadashi
T
Yamamoto
Takeshi
T
Yagi
Toshio
T
Hirano
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000276:immunology; D015550:Cell Degranulation / Q000502:physiology; D002462:Cell Membrane / Q000276:immunology*; D002478:Cells, Cultured; D005089:Exocytosis / Q000187:drug effects / Q000276:immunology; D018836:Inflammation Mediators / Q000276:immunology / Q000378:metabolism; D008407:Mast Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D008561:Membrane Fusion / Q000187:drug effects / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008870:Microtubules / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects / Q000276:immunology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051076:Proto-Oncogene Proteins c-fyn; D011940:Receptor Aggregation / Q000276:immunology; D017455:Receptors, IgE / Q000276:immunology*; D022142:Secretory Vesicles / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D020742:rhoA GTP-Binding Protein / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; C490894:Gab2 protein, mouse; D018836:Inflammation Mediators; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D017455:Receptors, IgE; C494960:Fyn protein, mouse; D051076:Proto-Oncogene Proteins c-fyn; D019061:src-Family Kinases; D020742:rhoA GTP-Binding Protein; D002118:Calcium