Abstract: Disclosed herein are eukaryotic host systems for producing recombinant proteins, eukaryotic hosts modified to produce recombinant proteins, and methods of producing recombinant proteins using the same. In certain embodiments, the eukaryotic host system is a plasmodium of the class Myxogastria, such as Physarum polycephalum, modified to produce one or more recombinant proteins, such as human insulin. In certain embodiments, a method of protein production includes collecting one or more recombinant proteins produced by Physarum polycephalum while in a form of multinucleate plasmodia.