Adipoyl Chloride

Introduction

A lipid molecule has long been known to aggregate into long-lived multivesicular endosomes (MVE), often called the "rafts," depending on their size and location within a cell. A new technique, inspired by MVE, reveals the way all cells store and synthesize lipids.

Scientists have long known that internalizing lipids on MVE gives them extraordinary opportunities for storage and secretion. But MVE have never been described as carrying lipid-coated vesicles before, as proposed by the Nobel Prize-winning lipid biochemist Yasunari Kato in 1988. A team led by Paul Twarm of the Max Planck Institute for Biophysical Chemistry in Göttingen, Germany, reveals that MVE carry coated vesicles-lipid molecules that spontaneously fuse into multivesicles (MVs).

What is a multivesicular body?

Multivesicular bodies (MVBs) are membranous organelles that harbor multiple, sometimes undifferentiated, lipid vesicles; they typically enclose the Golgi apparatus, the ER, and endosomes, according to biophysicist Martin Kay and colleagues at the California Institute of Technology in Pasadena, California. We typically think of Golgi as the central hub of the secretory pathway, because that's where much of the organelle's machinery is. But recent work has suggested that MVs containing internalized materials could come from more diverse regions of the cell, from the trans-Golgi network, the ER, the trans-Golgi, and endosomes.

For a long time we assumed that MVBs were cytoplasm-attached vesicles, just like cytoplasmic organelles. But the first indication was that certain bacterial cells lack Golgi apparatus. This strongly implied that MVBs might not come from the Golgi. In early 2008, we noticed that the secreted lipid precursor phosphatidylcholine (PC) crystallized into a powder that we thought was MVE. We took a look at the ultrastructure and immediately recognized that the crystals formed in "clusters" of nanometer-thin vesicles called multivesicular bodies (MVBs), and not just attached to the cytoplasmic membrane.