GRASP depletion–mediated Golgi destruction decreases cell adhesion and migration via the reduction of a5ß1 integrin

Ahat, Erpan; Xiang, Yi; Zhang, Xiaoyan; Bekier, Michael E.; Wang, Yanzhuang

Integrins are heterodimers consisting of α and β subunits, both of which are type I transmembrane proteins with a small cytosolic tail and a large extracellular domain. The best-characterized integrin complex in HeLa cells is the α5β1 integrin (Yu et al., 2011; Jia et al., 2016; Hang et al., 2017) , which mediates cell adhesion by binding to fibronectin, and this requires proper N-glycosylation of α5β1 integrin (Guo et al., 2002; Isaji et al., 2006) . Given the reduced binding of GRASP-depleted cells to fibronectin-coated plates (Figure 1 and Supplemental Figure 1 ), we further examined the effects of GRASP depletion on the protein level of α5 integrin using two antibodies that recognize the N-or C-terminus of the protein, or the heavy (∼130 kDa) or light (∼19 kDa) chain of the mature protein, respectively ( Figure 5B ). Depletion of GRASP proteins by siRNA, or knockout of GRASPs by CRISPR/cas9, both significantly reduced α5β1-integrin protein levels ( . In contrast to GRASP depletion, disruption of the Golgi structure by nocodazole (Noc) or brefeldin A (BFA) treatment had no effect on the protein level of α5β1 integrin (Supplemental Figure 4C ). In addition, disruption of the Golgi ribbon by Golgin 84 depletion had no effect on integrin level (Supplemental Figure 6 in Xiang et al., 2013) . These results indicate a unique role of Golgi stacking rather than ribbon linking in regulating integrin-mediated cell adhesion and migration.