TY - JOUR
T1 - Munc13 proteins control regulated exocytosis in mast cells
AU - Rodarte, Elsa M.
AU - Ramos, Marco A.
AU - Davalos, Alfredo J.
AU - Moreira, Daniel C.
AU - Moreno, David S.
AU - Cardenas, Eduardo I.
AU - Rodarte, Alejandro I.
AU - Petrova, Youlia
AU - Molina, Sofia
AU - Rendon, Luis E.
AU - Sanchez, Elizabeth
AU - Breaux, Keegan
AU - Tortoriello, Alejandro
AU - Manllo, John
AU - Gonzalez, Erika A.
AU - Tuvim, Michael J.
AU - Dickey, Burton F.
AU - Burns, Alan R.
AU - Heidelberger, Ruth
AU - Adachi, Roberto
N1 - Funding Information:
This work was supported by the National Institutes of Health Grants AI093533, HL129795, CA016672, EY007551, and EY018239 and the Cancer Prevention Research Institute of Texas Grant RP110166. The authors declare that they have no conflicts of interest with the contents of this article. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
PY - 2018/1/5
Y1 - 2018/1/5
N2 - Mast cells (MCs) are involved in host defenses against pathogens and inflammation. Stimulated MCs release substances stored in their granules via regulated exocytosis. In other cell types, Munc13 (mammalian homolog of Caenorhabditis elegans uncoordinated gene 13) proteins play essential roles in regulated exocytosis. Here, we found that MCs express Munc13-2 and -4, and we studied their roles using global and conditional knock-out (KO) mice. In a model of systemic anaphylaxis, we found no difference between WT and Munc13-2 KO mice, but global and MC-specific Munc13-4 KO mice developed less hypothermia. This protection correlated with lower plasma histamine levels and with histological evidence of defective MC degranulation but not with changes in MC development, distribution, numbers, or morphology. In vitro assays revealed that the defective response in Munc13-4-deficient MCs was limited to regulated exocytosis, leaving other MC secretory effector responses intact. Single cell capacitance measurements in MCs from mouse mutants differing in Munc13-4 expression levels in their MCs revealed that as levels of Munc13-4 decrease, the rate of exocytosis declines first, and then the total amount of exocytosis decreases. A requirement for Munc13-2 in MC exocytosis was revealed only in the absence of Munc13-4. Electrophysiology andEMstudies uncovered that the number of multigranular compound events (i.e. granule-to-granule homotypic fusion) was severely reduced in the absence of Munc13-4. We conclude that although Munc13-2 plays a minor role, Munc13-4 is essential for regulated exocytosis in MCs, and that this MC effector response is required for a full anaphylactic response.
AB - Mast cells (MCs) are involved in host defenses against pathogens and inflammation. Stimulated MCs release substances stored in their granules via regulated exocytosis. In other cell types, Munc13 (mammalian homolog of Caenorhabditis elegans uncoordinated gene 13) proteins play essential roles in regulated exocytosis. Here, we found that MCs express Munc13-2 and -4, and we studied their roles using global and conditional knock-out (KO) mice. In a model of systemic anaphylaxis, we found no difference between WT and Munc13-2 KO mice, but global and MC-specific Munc13-4 KO mice developed less hypothermia. This protection correlated with lower plasma histamine levels and with histological evidence of defective MC degranulation but not with changes in MC development, distribution, numbers, or morphology. In vitro assays revealed that the defective response in Munc13-4-deficient MCs was limited to regulated exocytosis, leaving other MC secretory effector responses intact. Single cell capacitance measurements in MCs from mouse mutants differing in Munc13-4 expression levels in their MCs revealed that as levels of Munc13-4 decrease, the rate of exocytosis declines first, and then the total amount of exocytosis decreases. A requirement for Munc13-2 in MC exocytosis was revealed only in the absence of Munc13-4. Electrophysiology andEMstudies uncovered that the number of multigranular compound events (i.e. granule-to-granule homotypic fusion) was severely reduced in the absence of Munc13-4. We conclude that although Munc13-2 plays a minor role, Munc13-4 is essential for regulated exocytosis in MCs, and that this MC effector response is required for a full anaphylactic response.
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U2 - 10.1074/jbc.M117.816884
DO - 10.1074/jbc.M117.816884
M3 - Article
C2 - 29141910
AN - SCOPUS:85040101940
SN - 0021-9258
VL - 293
SP - 345
EP - 358
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 1
ER -