Biology subjects

McCafferty, D. G.

Publications and source records attributed to McCafferty, D. G..

5 recordsLinked to original sources

bioRxiv2021

Investigation of the futalosine pathway for menaquinone biosynthesis as a novel target in the inhibition of Chlamydia trachomatis infection

Chlamydia trachomatis, an obligate intracellular bacterium with limited metabolic capabilities, possesses the futalosine pathway for menaquinone biosynthesis. Futalosine pathway enzymes have promise as narrow spectrum targets, but the activity and essentiality of chlamydial menaquinone biosynthesis have yet to be established. In this work, menaquinone-7 (MK-7) was identified as a C. trachomatis-produced quinone through LC-MS/MS. An immunofluorescence-based assay revealed that treatment of C. trachomatis-infected HeLa cells with futalosine pathway inhibitor docosahexaenoic acid (DHA) reduced inclusion number, inclusion size, and infectious progeny. Supplementation with MK-7 nanoparticles rescued the effect of DHA on inclusion number, indicating that the futalosine pathway is a target of DHA in this system. These results open the door for menaquinone biosynthesis inhibitors to be pursued in antichlamydial development.

biochemistry↗

bioRxiv2021

Chemoproteomic-enabled characterization of small GTPase Rab1a as a target of an N-arylbenzdiimidazole ligand's rescue of Parkinson's-associated cell toxicity

The development of phenotypic models of Parkinsons disease (PD) has enabled screening and identification of phenotypically active small molecules that restore complex biological pathways affected by PD toxicity. While these phenotypic screening platforms are powerful, they do not inherently enable direct identification of the cellular targets of promising lead compounds. To overcome this, chemoproteomic platforms like Thermal Proteome Profiling (TPP) and Stability of Proteins from Rates of Oxidation (SPROX) can be implemented to reveal protein targets of biologically active small molecules. Here we utilize both of these chemoproteomic strategies to identify targets of an N-arylbenzdiimidazole compound, NAB2, which was previously identified for its ability to restore viability in cellular models of PD-associated -synuclein toxicity. The combined results from our TPP and SPROX analyses of NAB2 and the proteins in a neuroblastoma-derived SHSY5Y cell lysate reveal a previously unrecognized protein target of NAB2. This newly recognized target, Rab1a, is a small GTPase that acts as a molecular switch to regulate ER-to-Golgi trafficking, a process that is disrupted by -synuclein toxicity and restored by NAB2 treatment. Further validation reveals that NAB2 binds to Rab1a with selectivity for its GDP-bound form and that NAB2 treatment phenocopies Rab1a overexpression in alleviation of -synuclein toxicity. Finally, we conduct a preliminary investigation into the relationship between Rab1a and the E3 ubiquitin ligase, Nedd4, a previously identified NAB2 target. Together, these efforts expand our understanding of the mechanism of NAB2 in the alleviation of -synuclein toxicity and reinforce the utility of chemoproteomic identification of the targets of phenotypically active small molecules that regulate complex biological pathways.

biochemistry↗

bioRxiv2020

Bioinformatic and computational analysis reveals the prevalence and nature of PY motif-mediated protein-protein interactions in the Nedd4 family of ubiquitin ligases

The Nedd4 family contains several structurally related but functionally distinct HECT-type ubiquitin ligases. The members of the Nedd4 family are known to recognize substrates through their multiple WW domains, which recognize PY motifs (PPxY, LPxY) or phospho-threonine or phospho-serine residues. To better understand substrate specificity across the Nedd4 family, we report the development and implementation of a python-based tool, PxYFinder, to identify PY motifs in the primary sequences of previously identified interactors of Nedd4 and related ligases. Using PxYFinder, we find that, on average, half of Nedd4 family interactions are PY-motif mediated. Further, we find that PPxY motifs are more prevalent than LPxY motifs and are more likely to occur in proline-rich regions. Further, PPxY regions are more disordered on average relative to LPxY-containing regions. Informed by consensus sequences for PY motifs across the Nedd4 interactome, we rationally designed a peptide library and employed a computational screen, revealing sequence- and biomolecular interaction-dependent determinants of WW-domain/PY-motif interactions. Cumulatively, our efforts provide a new bioinformatic tool and expand our understanding of sequence and structural factors that contribute to PY-motif mediated substrate recognition across the Nedd4 family.

biochemistry↗

bioRxiv2020

Characterization of small molecule induced changes in Parkinson's-related trafficking via the Nedd4 ubiquitin signaling cascade

The benzdiimidazole NAB2 rescues -synuclein-associated trafficking defects associated with early onset Parkinsons disease in a Nedd4-dependent manner. Despite identification of E3 ubiquitin ligase Nedd4 as a putative target of NAB2, its molecular mechanism of action has not been elucidated. As such, the effect of NAB2 on Nedd4 activity and specificity was interrogated through biochemical, biophysical, and proteomic analyses. NAB2 was found to bind Nedd4 (KDapp = 42 nM), but this binding is side chain mediated and does not alter its conformation or ubiquitination kinetics in vitro. Nedd4 co-localizes with trafficking organelles, and NAB2 exposure did not alter its colocalization. Ubiquitin-enrichment coupled proteomics revealed that NAB2 stimulates ubiquitination of trafficking and transport associated proteins, most likely through modulating the substrate specificity of Nedd4, providing a putative protein network involved in the NAB2 mechanism.

biochemistry↗

bioRxiv2020

Targeted Genome Mining Discovery of the Ramoplanin Congener Chersinamycin from the Dynemicin-Producer Micromonospora chersina DSM 44154.

The availability of genome sequence data combined with bioinformatic genome mining has accelerated the identification of biosynthetic gene clusters (BGCs). Ramoplanins and enduracidins are lipodepsipeptides produced by Actinoplanes ramoplaninifer ATCC 33076 and Streptomyces fungicidicus B-5477, respectively, that exhibit excellent in vitro activity against a broad spectrum of Gram-positive pathogens. To explore if ramoplanin/enduracidin-like BGCs exist within genomes of organisms sequenced to date, we devised a targeted genome mining strategy that employed structure-activity relationships to identify conserved, essential biosynthesis genes from the ramoplanin and enduracidin BGCs. Five microorganisms were found to contain ramoplanin-like BGCs: the enediyne antibiotic producer Micromonospora chersina strain DSM 44151(dynemycin); the glycopeptide antibiotic producers Amycolatopsis orientalis strain B-37 (norvancomycin), Amycolatopsis orientalis strain DSM 40040 (vancomycin), and Amycolatopsis balhimycina FH1894 strain DSM 44591 (balhimycin); and Streptomyces sp. TLI_053. A single compound from fermentation of M. chersina was purified to homogeneity and found to possess good antibiotic activity against several Gram-positive bacterial test strains (1-2 g/mL), comparing favorably to ramoplanin family members. We named this compound chersinamycin and elucidated its covalent structure, which differs distinctly from ramoplanins and enduracidins. Further, the chersinamycin BGC was validated through insertional gene inactivation using CRISPR-Cas9 gene editing. In addition to the information gained by comparing and contrasting the sequence and organization of these five new BGCs, the amenability of M. chersina to genetic manipulation provides a much-needed tool to investigate the fundamental aspects of lipodepsipeptide biosynthesis and to facilitate metabolic engineering efforts for the production of novel antibiotics capable of combating antibiotic-resistant infections.

bioinformatics↗