CREB activates proteasomal degradation of DSCR1/RCAN1.

The cyclic AMP response element-binding protein (CREB) is involved in the development and function of the nervous system. Here, we find that CREB decreases the protein level of Regulator of Calcineurin Activity 1 (RCAN1/DSCR1/MCIP1), which is overexpressed in the brain of Down Syndrome (DS) patients. Decrease of RCAN1 by CREB was blocked by proteasome inhibitors, indicating that this decrease is mediated by the ubiquitin-proteasome pathway. Furthermore, we found that the ability of CREB to activate the degradation of RCAN1 depends on its transcriptional activation. Consistently, CREB-enhanced the ubiquitination and turnover rate of RCAN1. Our results reveal a new regulatory role for CREB in DS pathology through the proteasomal degradation of RCAN1.