GFP Stable Cell Line-U937

Many extracellular proteins lack a signal peptide in their fundamental structure and so cannot be secreted by the conventional export pathway involving the endoplasmic reticulum (ER) and Golgi apparatus. The researchers looked at the nonclassical export mechanisms of signal peptide-less proteins. They found that stress-induced unconventional FGF1 export includes membrane bleb development and localized phosphatidylserine exposure on cell surfaces. Furthermore, differentiation of promonocytic cells causes significant FGF1 release, which correlates with membrane blebbing and phosphatidylserine exposure. These findings show that targeting externalized acidic phospholipids could be used to pharmacologically modulate FGF1 availability.

Figure 1. The researchers investigated FGF1 export mechanisms in U937 cells. They utilized U937 cells stably transfected with FGF1 and treated with 150 nM PMA for 48 h. BAPTA-AM treatment inhibited FGF1 export in a concentration-dependent manner. Over-expression of PLSCR1:GFP did not enhance FGF1 export, and shRNA knockdown of PLSCR1 did not affect it. These findings suggest that intracellular calcium, not PLSCR1, is crucial for FGF1 export from U937 cells. (Kirov A, et al., 2015)