Biomedical Engineering Reference
In-Depth Information
Chapter 1
Intracellular Parcel Service: Current Issues
in Intracellular Membrane Traffi cking
Johannes M. Herrmann and Anne Spang
Abstract
Eukaryotic cells contain a multitude of membrane structures that are connected through a highly dynamic
and complex exchange of their constituents. The vibrant instability of these structures challenges the clas-
sical view of defi ned, static compartments that are connected by different types of vesicles. Despite this
astonishing complexity, proteins and lipids are accurately transported into the different intracellular mem-
brane systems. Over the past few decades many factors have been identifi ed that either mediate or regulate
intracellular membrane traffi cking. Like in a modern parcel sorting system of a logistics center, the cargo
typically passes through several sequential sorting stations until it fi nally reaches the location that is speci-
fi ed by its individual address label. While each membrane system employs specifi c sets of factors, the trans-
port processes typically operate on common principles. With the advent of genome- and proteome-wide
screens, the availability of mutant collections, exciting new developments in microscope technology and
sophisticated methods to study their dynamics, the future promises a broad and comprehensive picture of
the processes by which eukaryotic cells sort their proteins.
Key words
Membrane traffi cking, Protein sorting, Protein translocation, Vesicular transport
1
Introduction
Cell Biology textbooks typically start with an illustration showing
a section through an eukaryotic cell, in which the different cellular
compartments are neatly ordered in a well-arranged and static
coexistence. In contrast, recent advances in high-resolution micros-
copy allowed exciting insights into the spatial, three-dimensional
orientation of cellular membranes showing that the cell is tightly
stuffed with a multitude of membrane structures (for examples
see
ref.
1
-
4
). Solely on the basis of their structural appearance, it is
almost impossible to attribute most of these membrane structures
to specifi c cellular compartments. Moreover, these membrane
structures are highly dynamic, constantly merging by fusion or
dividing by fi ssion, and always moving or are actively transported
