RAC1 and cancer: Lactate was recently found to shuttle to provide energy requirements and regulate functional signaling during cortical development.[43, 44] Previous studies have shown that Ldha interacts with GTPase‐Rac1, an activator of the p38MAPK pathway, in cancer cells.[45] We examined the interaction between Ldha and Rac1 by immunoprecipitation and showed that FLAG‐tagged Ldha pulls down HA‐tagged Rac1 (Figure 7M), indicating that there is an interaction between the 2 and that Ldha regulates the p38MAPK pathway by interacting with Rac1.