The stapled AKAP disruptor peptide STAD-2 displays antimalarial activity through a PKA-independent mechanism

Abstract

Drug resistance poses a significant threat to ongoing malaria control efforts. Coupled with lack of a malaria vaccine, there is an urgent need for the development of new antimalarials with novel mechanisms of action and low susceptibility to parasite drug resistance. Protein Kinase A (PKA) has been implicated as a critical regulator of pathogenesis in malaria. Therefore, we sought to investigate the effects of disrupted PKA signaling as a possible strategy for inhibition of parasite replication. Host PKA activity is partly regulated by a class of proteins called A Kinase Anchoring Proteins (AKAPs), and interaction between HsPKA and AKAP can be inhibited by the stapled peptide Stapled AKAP Disruptor 2 (STAD2). STAD2 was tested for permeability to and activity against Plasmodium falciparum blood stage parasites in vitro. The compound was selectively permeable only to infected red blood cells (iRBC) and demonstrated rapid antiplasmodial activity, possibly via iRBC lysis (IC 50 ≈ 1 μM). STAD2 localized within the parasite almost immediately posttreatment but showed no evidence of direct association with PKA, indicating that STAD2 acts via a PKAindependent mechanism. Furosemideinsensitive parasite permeability pathways in the iRBC were largely responsible for uptake of STAD2. Further, peptide import was highly specific to STAD2 as evidenced by low permeability of control stapled peptides. Selective uptake and antiplasmodial activity of STAD2 provides important groundwork for the development of stapled peptides as potential antimalarials. Such peptides may also offer an alternative strategy for studying proteinprotein interactions critical to parasite development and pathogenesis.