Here, we investigate regulation of coat protein complex II (COPII) recruitment onto ER export sites in perineabilized cells. In cytosols from nocodazole treated HeLa cells we find COPII loading is inhibited. The stress kinase p38 MAPK is activated in these cytosols and COPII loading can be rescued by depletion of p38 NIAPK alpha or by the p38 NIAPK inhibitor (SB203580) but not by inhibition/depletion of cdc2. These observations indicate regulation of the early secretory pathway by p38 NIAPK. Crown copyright (C) 2007 Published by Elsevier Inc. All rights reserved.