Leishmania Vesicle-Depleted Exoproteome: What, Why, and How?

Abstract

Leishmaniasis, a vector-borne parasitic protozoan disease, is among the most important neglected tropical diseases. In the absence of vaccines, disease management is challenging. The available chemotherapy is suboptimal, and there are growing concerns about the emergence of drug resistance. Thus, a better understanding of parasite biology is essential to generate new strategies for disease control. In this context, in vitro parasite exoproteome characterization enabled the identification of proteins involved in parasite survival, pathogenesis, and other biologically relevant processes. After 2005, with the availability of genomic information, these studies became increasingly feasible and revealed the true complexity of the parasite exoproteome. After the discovery of Leishmania extracellular vesicles (EVs), most exoproteome studies shifted to the characterization of EVs. The non-EV portion of the exoproteome, named the vesicle-depleted exoproteome (VDE), has been mostly ignored even if it accounts for a significant portion of the total exoproteome proteins. Herein, we summarize the importance of total exoproteome studies followed by a special emphasis on the available information and the biological relevance of the VDE. Finally, we report on how VDE can be studied and disclose how it might contribute to providing biologically relevant targets for diagnosis, drug, and vaccine development.

Keywords: Leishmania; exoproteome; exosomes; extracellular vesicles; leishmaniasis; secretome; vesicle-depleted exoproteome.

Figure 1

Schematic representation of the Leishmania spp. total exoproteome, secretome, extracellular vesicles (EVs), and vesicle depleted exoproteome (VDE) concepts. The exoproteome (blue rectangle) regroups all the secreted proteins as well as proteins that originated in the shedding of surface proteins or cell lysis; the secretome (pink rectangle) regroups all secreted proteins through conventional like the secreted acid phosphatases (SAPs) or non-classical pathways like the hydrophilic acylated surface protein B (HASPB); the EV fraction (green shaded rectangle) contains all vesicular components of the exoproteome, including those that originate from secretion, like the exosomes that are accumulated and released from the multivesicular bodies (MVBs) or from cellular lysis (dotted arrows); and the VDE (yellow shaded rectangle) contains all the non-vesicular components of the VDE, including those that originate from secretion, shedding from the surface, or lysis of cells or EVs (dotted arrows). The figure was created with BioRender.com.

Figure 2

Recovery approach used to compare different exoproteome fractions as proposed in [76]. PBS, phosphate-buffered saline.