Signal Transduction

Impaired B and T cell antigen receptor signaling in p110δ PI 3-kinase mutant mice.Okkenhaug, K. et al. Science 297, 1031–1034 (2002)

Class-IA phosphatidylinositol 3-kinases are composed of p85–p110 heterodimeric lipid kinases, and mammals express three isoforms of the catalytic p110 subunits. Researchers now show that mice expressing a catalytically inactive form of isoform p110δ are impaired in antigen-receptor signalling in both B and T cells, and that the immune response is weakened. This suggests that the other two isoforms are not crucial for antigen-receptor signalling.

Cytoskeleton

A role for regulated binding of p150Glued to microtubule plus ends in organelle transport.Vaughan, P. S. et al. J. Cell Biol. 158, 305–319 (2002)

Microtubule motor proteins are important for transport of cargo in the cell. In this report, Vaughan et al. studied the p150Glued subunit of the microtubule-associated protein dynactin using live-cell imaging of green fluorescent protein (GFP)–p150Glued fusions. They showed that dynactin interacts dynamically with growing microtubule plus ends, and that p150Glued phosphorylation regulates this interaction. Analysis of GFP-p150Glued together with motile Golgi membranes indicates that the dynamic binding of dynactin to microtubules plus ends is important in the early stages of membrane transport.

Technique

Visualization of maltose uptake in living yeast cells by fluorescent nanosensors.Fehr, M. et al. Proc. Natl Acad. Sci. USA 99, 9846–9851 (2002)

To study the compartmentation and transport of metabolites, sensitive but noninvasive in vivo monitoring techniques are needed. Fehr et al. now report such a technique based on fluorescent nanosensors. Periplasmic binding proteins are suitable candidates for this protein-based nanosensor, and maltose-binding protein was chosen as a prototype. The binding of solute substrate to maltose-binding protein results in increased fluorescence that can be measured in a concentration-dependent manner.

Cellular Microbiology

Helicobacter pylori SabA adhesin in persistent infection and chronic inflammation.Mahdavi, J. et al. Science 297, 573–578 (2002)

Helicobacter pylori bacteria adhere to the gastric surface epithelium using adhesins that interact with specific host-cell receptors. Mahdavi and colleagues now identify sialyl-dimeric-Lewis-X as a new adherence receptor, and SabA as its corresponding bacterial adhesin. They also show that persistent infection upregulates the expression of sialyl-Lewis-X antigens, which could explain the extraordinary persistence of H. pylori infection.