Centralspindlin is a motor complex implicated in cell division. It contributes to virtually every step in cytokinesis,[1] It is highly conserved in animal cells as a component of the spindle midzone and midbody.[2] Centralspindlin is required for the assembly of the mitotic spindle[3] as well as for microtubule bundling and anchoring of midbody microtubules to the plasma membrane.[1][2] This complex is also implicated in tethering the spindle apparatus to the plasma membrane during cytokinesis[4] This interaction permits cleavage furrow ingression. In addition, centralspindlin's interaction with the ESCRT III allows for abscission to occur.[1]
Structure
Centralspindlin is a heterotetramer consisting of two different subunit proteins:[1]
A KIF23 dimer (Kinesin 6 motor protein, also known as MKLP1 in mammals and ZEN-4 in C. elegans)
Consists of a motor domain linked to a parallel coiled coil and a globular region by a linker
A RACGAP1 dimer (Also known as MgcRacGAP in mammals or CYK-4 in C. elegans)
Contains a coiled-coil and an important RhoGAP domain
Both KIF23 and RacGAP1 dimerize via their parallel coiled coil domain.[2][5]
Centralspindlin oligomerizes in order to link the mitotic spindle with the plasma membrane[1] The sequences mediating interactions between KIF23 and RacGAP1 are highly variable between species. However, a high affinity interaction between these subunits is essential for the proper functioning of the Centralspindlin complex.[5]
Subunits
KIF23 interacts with microtubules at sites of overlap,[2] linking the centralspindlin complex to the mitotic spindle.
RacGAP1 recruits ECT2 to the central spindle.[3] ECT2 is a Guanine nucleotide-exchange factor for RhoA. Cytokinesis is initiated when RhoA is activated by ECT2.[6]
RacGAP1 is also involved in tethering the central spindle to the plasma membrane. Without this interaction, cytokinesis cannot occur.[4]
