Brefeldin A and GGTI-2133 were obtained from Sigma-Aldrich (St Louis, MO, USA). Professor David Wiemer at the University of Iowa kindly provided the GGDPSi VSW1198 [8 (link)] and RAM2061 [10 (link)], as well as the GGTase II inhibitor NHB2005 [31 (link)].