The secreted proteome profile of developing Dictyostelium discoideum cells

Abstract

Dictyostelium discoideum is a unicellular eukaryote that, when starved, aggregates to form multicellular structures. In this report, we identified the proteins secreted by developing Dictyostelium cells using MS-based proteomics. A total of 349 different secreted proteins were identified, indicating that at least 2.6% of the 13 600 predicted proteins in the Dictyostelium genome are secreted. Gene ontology analysis suggests that many of the secreted proteins are involved in protein and carbohydrate metabolism, and proteolysis.

Figure 1. Proteins secreted by developing Dictyostelium cells

(A) Experimental setup with wild-type cells on a porous membrane in contact with buffer. The developing cells aggregate and form fruiting bodies. During this period, molecules are secreted into the buffer. (B) Aliquots of the conditioned buffer were collected at the indicated times. Proteins in the conditioned buffer were separated by electrophoresis on a SDS-PAGE gel, which was then silver-stained.

Figure 2. The conditioned starvation buffer contains known secreted proteins

Proteins in the conditioned buffer were separated by electrophoresis on SDS-PAGE gels, and transferred to membranes. The membranes were then stained with affinity purified anti-CMF or anti-countin antibodies. The position of molecular mass markers (in kDa) is indicated at left.