CADM1 controls actin cytoskeleton assembly and regulates extracellular matrix adhesion in human mast cells.
CADM1 is a major receptor for the adhesion of mast cells (MCs) to fibroblasts, human airway smooth muscle cells (HASMCs) and neurons. It also regulates E-cadherin and alpha6beta4 integrin in other cell types. Here we investigated a role for CADM1 in MC adhesion to both cells and extracellular matrix (ECM). Downregulation of CADM1 in the human MC line HMC-1 resulted not only in reduced adhesion to HASMCs, but also reduced adhesion to their ECM. Time-course studies in the presence of EDTA to inhibit integrins demonstrated that CADM1 provided fast initial adhesion to HASMCs and assisted with slower adhesion to ECM. CADM1 downregulation, but not antibody-dependent CADM1 inhibition, reduced MC adhesion to ECM, suggesting indirect regulation of ECM adhesion. To investigate potential mechanisms, phosphotyrosine signalling and polymerisation of actin filaments, essential for integrin-mediated adhesion, were examined. Modulation of CADM1 expression positively correlated with surface KIT levels and polymerisation of cortical F-actin in HMC-1 cells. It also influenced phosphotyrosine signalling and KIT tyrosine autophosphorylation. CADM1 accounted for 46% of surface KIT levels and 31% of F-actin in HMC-1 cells. CADM1 downregulation resulted in elongation of cortical actin filaments in both HMC-1 cells and human lung MCs and increased cell rigidity of HMC-1 cells. Collectively these data suggest that CADM1 is a key adhesion receptor, which regulates MC net adhesion, both directly through CADM1-dependent adhesion, and indirectly through the regulation of other adhesion receptors. The latter is likely to occur via docking of KIT and polymerisation of cortical F-actin. Here we propose a stepwise model of adhesion with CADM1 as a driving force for net MC adhesion.
Institute for Lung Health, Dept. of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom.
Elena P
EP
Moiseeva
Centre for Core Biotechnology Services, University of Leicester, Leicester, United Kingdom.
Kees R
KR
Straatman
Department of Biochemistry, University of Leicester, Leicester, United Kingdom.
Mark L
ML
Leyland
Institute for Lung Health, Dept. of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom.
Peter
P
Bradding
D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D015153:Blotting, Western; D002448:Cell Adhesion / Q000187:drug effects; D000075982:Cell Adhesion Molecule-1; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D005109:Extracellular Matrix / Q000378:metabolism*; D006801:Humans; D007136:Immunoglobulins / Q000235:genetics / Q000378:metabolism*; D008407:Mast Cells / Q000166:cytology / Q000378:metabolism*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism; D010766:Phosphorylation; D058105:Polymerization; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D034622:RNA Interference; D012137:Respiratory System / Q000166:cytology; D013997:Time Factors; D014443:Tyrosine / Q000378:metabolism
D000199:Actins; C403514:CADM1 protein, human; D000075982:Cell Adhesion Molecule-1; D015815:Cell Adhesion Molecules; D002614:Chelating Agents; D007136:Immunoglobulins; D014443:Tyrosine; D004492:Edetic Acid; D019009:Proto-Oncogene Proteins c-kit