Targeting the ERAD pathway via inhibition of signal peptide peptidase for antiparasitic therapeutic design

Abstract

Early secretory and endoplasmic reticulum (ER)-localized proteins that are terminally misfolded or misassembled are degraded by a ubiquitin-and proteasome-mediated process known as ER-associated degradation (ERAD). Protozoan pathogens, including the causative agents of malaria, toxoplasmosis, trypanosomiasis, and leishmaniasis, contain a minimal ERAD network relative to higher eukaryotic cells, and, because of this, we observe that the malaria parasite Plasmodium falciparum is highly sensitive to the inhibition of components of this protein quality control system. Inhibitors that specifically target a putative protease component of ERAD, signal peptide peptidase (SPP), have high selectivity and potency for P. falciparum. By using a variety of methodologies, we validate that SPP inhibitors target P. falciparum SPP in parasites, disrupt the protein's ability to facilitate degradation of unstable proteins, and inhibit its proteolytic activity. These compounds also show low nanomolar activity against liver-stage malaria parasites and are also equipotent against a panel of pathogenic protozoan parasites. Collectively, these data suggest ER quality control as a vulnerability of protozoan parasites, and that SPP inhibition may represent a suitable transmission blocking antimalarial strategy and potential panprotozoan drug target.intramembrane proteolysis | small molecule | target validation

Identification of Cryptosporidium parvum Active Chemical Series by Repurposing the Open Access Malaria Box

“…A previously reported bioinformatic analysis concluded that p97 functions in the P. falciparum endoplasmic reticulum (ER)-associated degradation (ERAD) pathway, a streamlined protein quality-control pathway that is critical for the control of ER stress. Furthermore, pharmacologic interference with different proteins of the ERAD pathway (including p97 with DBeQ) in P. falciparum inhibits parasite growth (41). The aligned protein sequences of P. falciparum p97 (GenBank accession no.…”

Intramembrane proteases as drug targets

“…Interestingly, human SPP is involved in the maturation of the hepatitis C virus core protein [55], which is required for the production of viral particles [56,57]. In the malaria parasite P. falciparum, inhibition of SPP can block growth of the parasite [58], and may represent a future therapeutic strategy. The functions of the SPPL family members are still being uncovered [52].…”

Crosstalk between the Unfolded Protein Response and Pathways That Regulate Pathogenic Development inUstilago maydis

“…Abundance of spliced cib1 mRNA increased considerably when cells were treated with the ER stress inducing compounds tunicamycin (Tm) or DTT ( Figure 1B). In addition, we found increased expression of five conserved UPR target genes upon Tm or DTT treatment: um15034, which encodes a predicted homolog of the ER-resident chaperone Karyogamy Gene2/Binding Protein1 (Bip1; e-value: 0) (herein referred to as bip1) (Normington et al, 1989;Rose et al, 1989); um00904, which encodes a predicted homolog of yeast ER chaperone Luminal Hsp70 1 (Lhs1p) (e-value: 1.0e-49); um05352, which encodes a predicted homolog of yeast protein disulfide isomerase Multicopy Suppressor of PDH1 deletion1 (Mpd1p) (e-value: 6.0e-25); um10287, which encodes a predicted homolog of the yeast glycoprotein chaperone Calnexin1 (Cne1p) (e-value: 3.0e-65) (Travers et al, 2000); and um02729, which encodes a predicted homolog of the Plasmodium falciparum signal peptide peptidase Spp1 (e-value: 3.0e-46), known to be involved in the ER-associated degradation pathway in P. falciparum, Drosophila melanogaster, and Arabidopsis thaliana (Martinez and Chrispeels, 2003;Casso et al, 2012;Harbut et al, 2012) (Figure 1B;see Supplemental Figures 3A and 3B online).…”