Journal: bioRxiv
Article Title: ADAM10 tailors extracellular vesicles for content transfer rather than signaling by contact
doi: 10.64898/2026.02.12.705562
Figure Lengend Snippet: A. Volcano plot illustrating the proteins associated with GFP-SDC4 according to differential proteomics, with log2 fold change (x-axis) and -log10 (p-value) (y-axis). Data were obtained by GFP-pulldown from total extracts of MCF7 cells overexpressing GFP-SDC4 compared to MCF7 cells overexpressing GFP alone. Data result from three different experiments processed three times. SDC4 (the bait) is represented in green, ADAM10 and ADAM17, the two metalloproteases associated with SDC4 are represented in red. The other proteins are represented in grey. The proteins showing non-significant differences are represented below the dotted lines (threshold at 1 for the x-axis, difference =2 and 1.5 for y-axis; p-value = 0.3). B. Co-immunoprecipitation experiments from MCF7 cell lysates, confirming the association of endogenous ADAM10 and ADAM17 with GFP-SDC4, but not GFP. The GFP precipitates (IP) were subjected to Western blot with antibodies recognizing proteins as indicated on the right. C . Left: Scheme illustrating the complexity of SDC4 structure and processing. (Upper part) SDC4 full-length (FL) core protein (black) is substituted with glycosaminoglycan chains (GAG) of the heparan sulfate type (green). The trimming of GAG chains by specific enzymes is necessary for the FL protein to migrate at a discrete band in SDS-PAGE and to be easily detectable by immunoblotting. (Lower part) SDC4 core protein can be cleaved by proteases generating two main fragments: an N-terminal fragment comprising most of the GAG-substituted extracellular domain (ECD) and a C-terminal fragment (CTF) comprising the remainder of the ECD, the membrane-spanning and the cytoplasmic domain. Right: Western blot illustrating the signals obtained, after GAG-digestion, for FL SDC4 and SDC4 CTF in the cells and the sEV enriched fraction obtained after differential ultracentrifugation of the conditioned extracellular media. Signals were obtained with an antibody recognizing the intracellular domain of SDC4. Note that the FL form of SDC4 (SDC4-FL) abounds in cell lysates, while the CTF is less abundant. On the contrary, the SDC4-CTF is abundant and the SDC4-FL is barely detectable in sEVs. D. MCF7 cells downregulated for ADAM10 (siADAM10) or ADAM17 (siADAM17) and control cells (siCTRL) were evaluated for SDC4 FL and CTF abundance in cells and sEVs by Western blot after GAG-digestion. Histograms represent the mean signal intensity for indicated proteins relative to the signal in control cells, ± SEM. Statistical analysis was performed using the Kruskal-Wallis one-way non-parametric ANOVA test (* P < 0.05, *** P < 0.001, n.s. non-significant). E . sEVs secreted by MCF7 cells inhibited for ADAM10 activity, (GI254023X) versus controls (DMSO) were isolated from conditioned media by differential ultracentrifugation. sEVs were analyzed by Western blot after GAG-digestion to evaluate the levels of SDC4 FL and CTF. Histograms represent the mean signal intensity for indicated proteins relative to the signal in control cells, ± SEM. ** P < 0.01 (unpaired non-parametric Mann–Whitney test).
Article Snippet: To enzymatically digest the glycosaminoglycans (GAGs) on SDC, including heparan sulfate (HS) and chondroitin sulfate (CS), nine volumes of cell extract or EVs were incubated with one volume of 10x heparitinase reaction buffer (1M NaCl, 500mM hepes pH 7,0, 10mM CaCl2, 1% TX100, Pepstatin and Leupeptin, both at a concentration of 10 μg/mL), heparitinase (0.4 milliIU, amsbio), and chondroitinase (20milliunits, amsbio).
Techniques: Immunoprecipitation, Western Blot, SDS Page, Membrane, Control, Activity Assay, Isolation, MANN-WHITNEY