Volume 10 Issue 9, September 2009

Clathrin-mediated endocytosis dynamically regulates the composition of the plasma membrane in eukaryotic cells by internalizing transmembrane proteins, bound ligands and lipids. To regulate the uptake of a vast array of cargo molecules, specific sorting signals in cargoes are decoded by different cytosolic adaptor proteins.

Studies of cargo proteins that are internalized independently of clathrin have revealed new pathways and mechanisms of endocytic recycling. Precise temporal and spatial regulation of recycling pathways is crucial for various cellular processes, including cytokinesis, cell adhesion, morphogenesis, cell fusion, learning and memory.

It is now recognized that cell signalling and endocytic membrane trafficking are intimately and bidirectionally linked in animal cells. The mechanistic and functional principles that underlie the relationship between these cellular processes are becoming increasingly evident across many systems.

Lysosomes are the primary catabolic compartments of eukaryotic cells. They degrade extracellular material that has been internalized by endocytosis and intracellular components that have been sequestered by autophagy. Emerging evidence suggests that there are multiple lysosomal delivery pathways that together allow the regulated and sequential deposition of lysosomal components.

Natural antisense transcripts are frequently functional and are involved in regulating gene expression. The authors summarize the proposed actions of antisense transcript into four models, each corresponding to a putative regulatory mechanism for a subset of antisense transcripts.

The reconstitution of biological processes from purified components is a powerful approach to understanding the principles that govern cellular organization. The recent development of new experimental techniques is enabling the reconstitution of increasingly complex cellular systems.