Nucleocytoplasmic transport under stress conditions and its role in HSP70 chaperone systems

Background: In eukaiyotic cells, molecular trafficking between the nucleus and cytoplasm is a highly regulated process related to cellular homeostasis and cellular signaling. However, various cellular stresses induce the perturbation of conventional nucleocytoplasmic transport pathways, resulting in the nucleocytoplasmic redistribution of many functional proteins. Scope of review: We describe the recent insights into the mechanism and functions of nuclear import of cytosolic chaperone HSP70 under stress conditions and the cellular distribution and functions of its co-chaperones. Major conclusions: Hikeshi mediates the nuclear import of the molecular chaperone HSP70. A few of the regulators of the HSP70 chaperone system also accumulate in the nucleus under heat stress conditions. These proteins function collaboratively to protect cells from stress-induced damage and aid in the recovery of cells from stress. General significance: Studies on the regulation of nucleocytoplasmic transport under several cellular stresses should provide new insights into the fundamental principles of protein homeostasis (proteostasis) in both compartments, the nucleus and cytoplasm. (C) 2014 Elsevier B.V. All rights reserved.