Proposed mechanism by which PRL may affect CPT1 enzyme activity in breast cancer cells. PRL signaling may alter CPT1 enzyme activity in two distinct manners, with potential cross-talk. In 1), PRL mediates its effect through LKB1, resulting in activation of the AMPK pathway via phosphorylation of AMPKα at Thr172 (pAMPKα) and inactivation of ACC (pACC), culminating in increased CPT1 enzyme activity. In 2), PRL either directly, or indirectly through the activation of AMPK, induces PPARα to increase CPT1A expression, resulting in changes at both the mRNA and protein levels, thereby increasing CPT1 enzyme activity. Dashed arrows and ?s indicate components of the pathway(s) that remain to be conclusively established.