RPS6KB1 and systemic sclerosis: Indeed, exposure of HMECs to SSc-IgG at a dose of 1 mg/mL resulted in an approximately 2-fold increase in the expression of phosphorylated pAKT (a central effector of the PI3K pathway upstream of mTORC1), p70S6K (a substrate for the mTOR pathway) and pERK1/2 (Figure 4).