PKC activity is decreased, and the PKC activator can attenuate cognitive impairment and proinflammatory signals in APP/PS1 transgenic mice.12, 35 ɑ‐synuclein overexpression could decrease PKC and ERK activity, which further inhibits CREB transcription.34 PKC mediates retinoic acid induction of DARPP32 in medium‐sized spiny neurons, which is decreased in human HD. Here, CREB1 is linked to Huntington disease.