During exocytosis and vesicle trafficking membrane fusion is mediated by a suite of proteins highly conserved throughout eukaryotes. Membrane specific tethering and priming, initiated by Rab GTPases, brings vesicle and target membranes in close proximity allowing trans interaction between corresponding vesicle (v)-SNAREs and target (t)-SNAREs. Further protein interactions and membrane modifications lead to fusion of membranes and release of vesicle contents resulting in cis-pairing of v-SNAREs and t-SNAREs in the same membrane. αSoluble NSF Attachment Protein (αSNAP) is required for recycling of cis-SNARE complexes, through recruitment of ATPase N-ethylmaleimide sensitive factor (NSF), to recharge the cellular pool of SNAREs for further trafficking events.
Apicomplexan are obligate intracellular pathogens that absolutely require invasion into host cell for survival and as such have evolved specialized invasion machinery. During replication, these parasites utilize the secretory pathway for inner membrane complex (IMC) and plasma membrane (PM) biogenesis as well as de novo synthesis of apical invasion organelles. Utilising T.gondii, modulation of key phosphorylation sites on αSNAP allows us to interfere with endogenous αSNAP processes with a regulated dominant negative system. We have shown that ablation of normal αSNAP functions leads to severely disrupted secretory systems lethal to the parasite. Cytokenesis, de novo apical organelle, PM and IMC biogenesis are all disordered while secretory-independent mechanisms, such as karyokenesis are not directly affected. Protein processing and localisation are also abnormal.
Understanding of molecular trafficking mechanisms in Apicomplexa, especially those related to the unique invasion organelles, can aid our understanding of these parasites and inform future drug and vaccine designs.