ABSTRACT
Biological systems exchange water and various other molecules with
the environment across membranes. The direction and lux of water and
solutes are determined by subcellular distribution of various channels
and transporters. These membrane-bound proteins are freely diffusible in
principle, but in cells their distribution is asymmetrical and nonhomogeneous
for functional reasons. Membrane proteins are organized mainly by three
cellular processes: (i) vesicle transport that targets the membrane proteins
to speciic membrane domains, (ii) containment of the proteins within each
membrane domain by diffusion barriers, and (iii) tethering of the proteins at
narrower subdomains by scaffolds. The cytoskeleton plays essential roles in
each process; microtubules provide tracks for directed vesicle transport, while
an actin meshwork beneath the plasma membrane provides a framework for
the diffusion barriers and scaffolds. Getting an overview of these processes,
this chapter focuses on the unique roles of the septin cytoskeleton, which
helps organize the transport system in conjunction with the microtubule and
actin cytoskeleton.
