Moiseeva Elena P, Straatman Kees R, Leyland Mark L, Bradding Peter
Institute for Lung Health, Dept. of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom.
Centre for Core Biotechnology Services, University of Leicester, Leicester, United Kingdom.
PLoS One. 2014 Jan 22;9(1):e85980. doi: 10.1371/journal.pone.0085980. eCollection 2014.
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.
CADM1是肥大细胞（MCs）与成纤维细胞、人气道平滑肌细胞（HASMCs）和神经元黏附的主要受体。它还在其他细胞类型中调节E-钙黏蛋白和α6β4整合素。在此，我们研究了CADM1在MC与细胞及细胞外基质（ECM）黏附中的作用。在人MC系HMC-1中下调CADM1不仅导致其与HASMCs的黏附减少，还导致其与ECM的黏附减少。在存在乙二胺四乙酸（EDTA）以抑制整合素的情况下进行的时间进程研究表明，CADM1提供了对HASMCs的快速初始黏附，并辅助了对ECM的较慢黏附。CADM1下调而非抗体依赖性CADM1抑制降低了MC与ECM的黏附，提示对ECM黏附的间接调节。为了研究潜在机制，我们检测了整合素介导黏附所必需的磷酸酪氨酸信号传导和肌动蛋白丝的聚合。CADM1表达的调节与HMC-1细胞表面KIT水平和皮质F-肌动蛋白的聚合呈正相关。它还影响磷酸酪氨酸信号传导和KIT酪氨酸自身磷酸化。CADM1占HMC-1细胞表面KIT水平的46%和F-肌动蛋白的31%。CADM1下调导致HMC-1细胞和人肺MCs中皮质肌动蛋白丝伸长，并增加了HMC-1细胞的细胞刚性。总体而言，这些数据表明CADM1是一种关键的黏附受体，它通过CADM1依赖性黏附直接调节MC净黏附，并通过调节其他黏附受体间接调节。后者可能通过KIT的对接和皮质F-肌动蛋白的聚合发生。在此，我们提出了一个以CADM1为MC净黏附驱动力的逐步黏附模型。
