A Barrier to Lateral Diffusion in the Cleavage Furrow of Dividing Mammalian Cells

Abstract

Barriers to diffusion of proteins and lipids play an important role in generating functionally specialized regions of the plasma membrane. Such barriers have been reported at the base of axons, at the bud neck in Saccharomyces cerevisiae, as well as at the tight junctions of epithelia. How diffusion barriers are formed and how they effect behavior of both inner and outer leaflets of the bilayer are not fully understood. Here, we provide evidence for a cortical barrier to diffusion within the cleavage furrow of mammalian cells. Photobleaching-based assays were used to measure diffusion of three membrane proteins with differing topologies and putative lipid raft association, as well as the lipid analog dialkylindocarbocyanine (DiI C18, ), across the cleavage furrow. There was a block in diffusion of proteins with a cytosolic domain, but not of proteins anchored in the outer leaflet of the PM or of DiI. Diffusion of lipid raft proteins in the inner and outer leaflets of the membrane was not directly coupled. The distribution of Septin proteins, as opposed to cortical actin, was consistent with a functional role in limiting diffusion.

Ruffles limit diffusion in the plasma membrane during macropinosome formation

“…Diffusion barriers have been previously identified in cleavage furrows (Schmidt and Nichols, 2004) and in the leading edge of cellular protrusions (Weisswange et al, 2005). Whereas those structures result from larger changes in cell morphology, macropinocytic circular ruffles are self-organized.…”

Zygotically controlled F-actin establishes cortical compartments to stabilize furrows duringDrosophilacellularization

“…The establishment of compartments around the cortical Factin/Myosin 2 array appears to be a conserved feature of furrowing during conventional cytokinesis, common from yeast (Dobbelaere and Barral, 2004;Takeda et al, 2004;Wachtler et al, 2003), to sea urchin and Xenopus embryos (Byers and Armstrong, 1986), to cultured mammalian cells (Schmidt and Nichols, 2004). Previous analyses in cellularizing Drosophila embryos similarly suggested that the F-actin/Myosin 2 furrow canals are discrete compartments that form at the tips of incipient furrows and are maintained as the furrows ingress (Lecuit and Wieschaus, 2000).…”

Some assembly required: yeast septins provide the instruction manual

“…This compartmentalization function appears to be conserved in fission yeast, where a double ring of septin filaments encompasses the contractile apparatus and provides for efficient dissolution of the primary septum [32,33]. It appears that septins might have a similar role in mammalian cells because septins are prominent components of the cleavage furrow and a diffusion barrier within the cleavage furrow has been demonstrated [34].…”