Biology subjects

Lamb, I. M.

Publications and source records attributed to Lamb, I. M..

3 recordsLinked to original sources

bioRxiv2025

ATAD3 megadalton complex in Plasmodium falciparum is essential for mitochondrial and cellular viability

Malaria remains an urgent threat to global health as the mortality and infection rates keep rising annually and our frontline antimalarials are becoming less effective due to the emergence and spread of resistance-conferring mutations. Although the mitochondrion of P. falciparum parasites is a validated drug target, there remain many uncharacterized mitochondrial proteins. The goal of this study was to investigate the essentiality and functions of a recently identified mitochondrial protein - PF3D7_0707400. Our results show that PF3D7_0707400 is an ATAD3A ortholog that is essential to parasite survival and is present in a megadalton complex that is critical for multiple mitochondrial processes such as mitochondrial RNA stability, membrane potential, ultrastructure, and protein import. This study is the first characterization, to our knowledge, of ATAD3A in unicellular organisms. ATAD3A has been previously studied in multicellular eukaryotes and has been implicated in several childhood mitochondrial diseases. Our findings here expand our knowledge on apicomplexan mitochondrial biology and our arsenal of potential antimalarial drug targets. Author SummaryEach year, malaria is responsible for about 200 million infections and 600,000 deaths across the world. Thus, it constitutes a huge global health crisis. Increasing rates of antimalarial resistance necessitates the identification and characterization of novel parasitic proteins that can be exploited for the development of new antimalarial therapeutics. To this end, the mitochondrion of P. falciparum parasites has been studied as a validated target for effective antimalarials. However, much remains to be understood about critical mitochondrial processes and proteins that are essential for mitochondrial viability and parasite survival. Our study details the first characterization of an ATAD3 protein in a unicellular eukaryote, specifically in an apicomplexan parasite. The conservation of this protein in these deep-branching organisms highlights the importance of its biological functions, further emphasizing the significance of our study. By employing advanced molecular biology techniques, we show the presence of PfATAD3 in a giant molecular complex and its essentiality in asexual P. falciparum parasites. Conditional knockdown of PfATAD3 resulted in defects in critical mitochondrial processes such as mitochondrial RNA stability, mitochondrial membrane potential, and mitochondrial morphology. Divergence of PfATAD3 from the host allows for exploitation of this protein as a target for new antimalarials.

microbiology↗

bioRxiv2025

Differential role of phosphorylation in glucagon family receptor signaling revealed by mass spectrometry

In response to extracellular ligands, G protein-coupled receptors (GPCRs) undergo conformational changes that induce coupling to intracellular effectors such as heterotrimeric G proteins that trigger various downstream signaling pathways 1. These events have been shown to be highly regulated by the concerted effects of post-translational modifications (PTMs) that occur in a ligand-dependent manner. Most notably, phosphorylation of residues in the C-terminal cytoplasmic tail of GPCRs has been strongly implicated in promoting receptor interactions with {beta}-arrestins ({beta}arrs) 2, 3 which are cytosolic adaptor proteins that modulate G protein coupling 4, receptor internalization 5, and perhaps also serve as signaling modules in their own right 6. Here, we use proteomic methods to identify C-tail residues that are phosphorylated in the glucagon family of class B1 GPCRs (GLP-1R, GCGR, GIPR) upon agonist addition. Mutagenesis studies reveal unique effects of phosphorylated residues on {beta}arr recruitment and cyclic AMP (cAMP) production that occur in a receptor-dependent manner. We demonstrate that phosphorylation of GLP-1R and GIPR is a critical determinant in driving the formation of GPCR-{beta}arr complexes. However, our results suggest that ligand-induced {beta}arr recruitment to the GCGR proceeds in a phosphorylation-independent manner. These findings highlight the importance of recognizing phosphorylation as a component in the regulation of class B1 GPCR signaling, but also the need to consider how such phenomena may not necessarily yield identical effects on intracellular signaling cascades.

pharmacology and toxicology↗

bioRxiv2022

Mitochondrially targeted proximity biotinylation and proteomic analysis in Plasmodium falciparum

Despite ongoing efforts to control malaria infection, progress in lowering the number of deaths and infections appears to have stalled. The continued high incidence of malaria infection and mortality is in part due to emergence of parasites resistant to frontline antimalarials. This highlights the need for continued identification of novel protein drug targets. Mitochondrial functions in Plasmodium falciparum, the deadliest species of human malaria parasite, are targets of validated antimalarials including atovaquone and proguanil (Malarone). Thus, there has been great interest in identifying other essential mitochondrial proteins as candidates for novel drug targets. Garnering an increased understanding of the proteomic landscape inside the P. falciparum mitochondrion will also allow us to learn about the basic biology housed within this unique organelle. We employed a proximity biotinylation technique and mass spectrometry to identify novel P. falciparum proteins putatively targeted to the mitochondrion. We fused the leader sequence of a mitochondrially targeted chaperone, Hsp60, to the promiscuous biotin ligase TurboID. Through these experiments, we generated a list of 122 "putative mitochondrial" proteins. To verify whether these proteins were indeed mitochondrial, we chose five candidate proteins of interest for localization studies using ectopic expression and tagging of each full-length protein. This allowed us to localize four candidate proteins of unknown function to the mitochondrion, three of which have previously been assessed to be essential. We suggest that phenotypic characterization of these and other proteins from this list of 122 could be fruitful in understanding the basic mitochondrial biology of these parasites and aid antimalarial drug discovery efforts.

microbiology↗