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Access through your institution Buy or subscribe Rab proteins are involved in a multitude of membrane traffic and fusion events, including the endocytic pathway. They cycle between active

(GTP-bound) and inactive (GDP-bound), as well as between membrane-bound and cytosolic states. The latter cycle is regulated by RabGDI, which extracts GDP-bound Rab proteins from the

membrane, allowing their recycling to and subsequent activation at the next membrane. Both cycles are thought to ensure the directionality of membrane traffic. Cavalli _et al_. searched for

an upstream regulator of RabGDI that would increase its capacity to extract Rab5—a Rab protein involved in early steps of endocytic transport—from endosomal membranes. The activity they

identified was stress-activated p38 kinase, which directly phosphorylates serine 121 of RabGDI. In intact cells, the p38 pathway can be activated by various cellular stresses, such as

oxidative stress or UV irratiation. Under stress situations, Rab5 and its effector EEA1 were released from endosomes, and this depends on the presence of serine 121 in RabGDI. The image

shows that the association of EEA1 (red) with endosomes is resistant to H2O2-induced release in the presence of the RabGDI S121A mutant (co-transfected with a GFP construct (green) to label

transfected cells). Most importantly, exposure of cells to UV light or H2O2 increased the rate of endocytosis in normal cells but not in cells lacking p38. Furthermore, basal levels of p38

activity seem to be required for the basal rate of endocytosis. Taken together, these data point to the existence of a pathway that links p38 and RabGDI to both constitutive endocytic

membrane transport and its regulation in response to external stress stimuli. This is a preview of subscription content, access via your institution ACCESS OPTIONS Access through your

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our FAQs * Contact customer support Authors * Barbara Marte View author publications You can also search for this author inPubMed Google Scholar RIGHTS AND PERMISSIONS Reprints and

permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Marte, B. Stressing endocytosis. _Nat Cell Biol_ 3, E92 (2001). https://doi.org/10.1038/35070154 Download citation * Issue Date: April 2001 *

DOI: https://doi.org/10.1038/35070154 SHARE THIS ARTICLE Anyone you share the following link with will be able to read this content: Get shareable link Sorry, a shareable link is not

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