P21

P21 acts by modulating the CNTF signaling pathway specifically targeting the gp130 and LIFRβ receptor complex that mediates CNTF's neurotrophic effects. By binding to the CNTF receptor interface P21 activates JAK-STAT signaling in neural stem cells promoting their proliferation and differentiation into neurons particularly in the hippocampal dentate gyrus — the primary site of adult neurogenesis. P21 also upregulates BDNF expression and reduces the activity of inhibitory factors that suppress neural stem cell division. The result is enhanced hippocampal neurogenesis which correlates with improvements in spatial memory pattern separation and cognitive flexibility in animal models. P21 appears to have a particularly strong effect on new neuron survival and integration into existing neural circuits.