Coupling of cortical dynein and Galpha proteins mediates spindle positioning in Caenorhabditis elegans

Despite being essential for spatial cell division control, the mechanisms governing spindle positioning remain incompletely understood. In the Caenorhabditis elegans one-cell stage embryo, the spindle becomes asymmetrically positioned during anaphase through the action of as-yet unidentified cortical force generators that pull on astral microtubules and that depend on two Galpha proteins and associated proteins. We performed spindle-severing experiments following temporally restricted gene inactivation and drug exposure, and established that microtubule dynamics and dynein are both required for generating efficient pulling forces. We found that the Galpha-associated proteins GPR-1/2 and LIN-5 interact in vivo with LIS-1, a component of the dynein complex. Moreover, we discovered that the LIN-5, GPR-1/2 and the Galpha proteins promote the presence of the dynein complex at the cell cortex. Our findings suggest a mechanism by which the Galpha proteins enable GPR-1/2 and LIN-5 recruitment to the cortex, thus ensuring the presence of cortical dynein. Together with microtubule dynamics, this allows pulling forces to be exerted and proper cell division to be achieved.