Lung-specific MCEMP1 functions as an adaptor for KIT to promote SCF-mediated mast cell proliferation

Lung mast cells are important in host defense, and excessive proliferation or activation of these cells can cause chronic inflammatory disorders like asthma. Two parallel pathways induced by KIT–stem cell factor (SCF) and FcεRI–immunoglobulin E interactions are critical for the proliferation and activation of mast cells, respectively. Here, we report that mast cell-expressed membrane protein1 (MCEMP1), a lung-specific surface protein, functions as an adaptor for KIT, which promotes SCF-mediated mast cell proliferation. MCEMP1 elicits intracellular signaling through its cytoplasmic immunoreceptor tyrosine-based activation motif and forms a complex with KIT to enhance its autophosphorylation and activation. Consequently, MCEMP1 deficiency impairs SCF-induced peritoneal mast cell proliferation in vitro and lung mast cell expansion in vivo. Mcemp1-deficient mice exhibit reduced airway inflammation and lung impairment in chronic asthma mouse models. This study shows lung-specific MCEMP1 as an adaptor for KIT to facilitate SCF-mediated mast cell proliferation.

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Source data are provided with this paper. RNA-seq data generated in this study have been deposited in the GEO database under accession code GSE197042; Subseries, GSE197040 (lung) and GSE197041 (PCMC).
No statistical methods were used to predetermine sample size. Instead sample size was determined based on the numbers required to generate statistical power and preliminary experiments. A small pilot experiment showed biologically significant results and so a larger scale experiment was performed based on results from pilot experiment.
No data were excluded from the analyses.
All experiments were repeated at least twice to ensure reproducibility of findings. Details are clearly indicated in each figure legend.
All samples were assigned to groups randomly.
During sample collection and processing and downstream analysis, there was no subjective component. Note that full information on the approval of the study protocol must also be provided in the manuscript. All the antibodies have been validated for the species and application following information provided by the manufacturer, and titrated using appropriate positive and negative controls, using different antibody dilutions. Further information on antibodies for immunoblotting is presented in Supplementary Table 3. 293T, Raw264.7, HMC-1 cells were purchased from ATCC. C57 and DC2.4 cells were kindly provided by S.J. Galli and K.L. Rock, respectively.
None of the cell lines used have been authenticated.
All cell lines were tested negative for mycoplasma contamination.
No commonly misidentified cell lines were used.
Mcemp1-/-mice (C57BL/6) were generated by CRISPR-Cas9 system. B6D2F1 (C57BL/6 X DBA2) foster female mice were used. Details are reported in Methods. Mice were maintained in a barrier facility for animals in a temperature-controlled system characterized by 22 Celsius degrees and 50% humidity, with a 12 hours dark/light cycle within cages.
No wild animals were used in the study.
male and female mice of equal distribution were used.
No field collected samples were used in the study.
All mice were bred and housed in specific pathogen free facilities maintained by the USC Animal Research Center at Keck Medical School and Cleveland Clinic Lerner Research Institute. All animal experiments were reviewed and approved by Institutional Animal Care and Use committees (IACUC) and Institutional Biosafety Committee (IBC) at USC and Cleveland Clinic.