Researchers stumble on cell's neatest little tricks

Washington, Dec 22 (IANS) Researchers have solved one of our bodies' neatest little tricks - how a cell pinches molecules from outside without allowing any leakage ot its membranes.

'Doing this without leaking is quite a feat,' said Sandra Schmid, who heads Scripps Research department of cell biology and co-authored the paper with Thomas Pucadyil, a postdoctoral researcher in her lab.

'A cell's outside environment is very nasty, and if any of that toxic fluid got into the cell, it would kill it,' added Schmid.

Scientists described creating a system in which they can watch, in real time under a light microscope, cell membranes bud and then pinch off smaller sack-like 'vesicles', said a Scripps statement. The findings are being featured in a forthcoming edition of the journal Cell.

This process is only possible, Scripps scientists said, because a single molecule, dynamin, forms a short 'collar' of proteins around a bit of the membrane that has emerged from the 'parent' membrane, and then squeezes it tight, cleanly separating the new 'daughter' vesicle.

The findings contradict the prevailing notion of how these vesicles are tied off from the membrane, and also suggest that this elegant little action may be ubiquitous throughout the cell, which must form millions of vesicles to move molecules between membrane organelles within the cell.

In this process, called endocytosis, cells take up materials (including hormones, nutrients, antibodies, and fats such as cholesterol) from the bloodstream by engulfing them in inward folds of the cell membrane that then close up, pinch off, and move into the cell as the cargo-laden vesicles.