Discovery of an Atypical Arp2/3 Complex in Malaria Parasites Sheds New Light on Nuclear Actin.

The Arp2/3 complex is a key actin nucleator essential for cytoskeletal dynamics in eukaryotes. Previously believed absent in apicomplexan parasites, we recently identified an atypical Arp2/3 complex in malaria parasites consisting of five divergent subunits and a putative kinetochore-associated factor. This complex ensures proper kinetochore-spindle attachment during male gametogenesis, likely by nucleating actin at the mitotic spindle. Disruption of Arp2/3 function or actin polymerization leads to defective DNA segregation into gametes and developmental arrest of the parasite in the mosquito. Our findings reveal unexpected diversity in Arp2/3 complex composition and function, highlighting specialized adaptations in malaria parasites and expanding our understanding of the Arp2/3 complex and actin functions during mitosis. Here, we discuss some of the open questions that need to be addressed to fully understand the molecular mechanism of this unusual Arp2/3 complex and its essential role in malaria transmission.