Biology subjects

Zeng, Z. W.

Publications and source records attributed to Zeng, Z. W..

4 recordsLinked to original sources

bioRxiv2026

Differential Nucleotide Inhibition Profile of Mouse and Human UCP1 Expressed in Liver Mitochondria Is Associated with an F88S Mutation

Uncoupling protein 1 (UCP1) mediates thermogenesis in brown adipose tissue. Whether human-UCP1 shares the bioenergetic properties established for rodent UCP1 (innate uncoupling, GDP sensitivity, fatty acid (re)activation) is not known. Therefore, we expressed human and mouse UCP1 in mouse liver, using adeno-associated viral vectors, and characterized their properties in isolated liver mitochondria. Both UCP1s induced marked innate uncoupling, characterized by increased substrate-supported respiration and decreased membrane potential, in the absence of exogenous fatty acids. Mouse-UCP1 in liver retained the classical regulatory properties of native brown-fat UCP1, including potent inhibition by GDP and reactivation by oleate. In contrast, human-UCP1 was only weakly inhibited by GDP but was strongly responsive to fatty acids. However, ATP potently inhibited human-UCP1, with an apparent IC of {approx}0.4 mM compared with {approx}1.4 mM for GDP, and ATP markedly decreased the sensitivity of human-UCP1 to oleate (re)activation. Despite substantial UCP1-mediated uncoupling, oxidative phosphorylation capacity and mitochondrial OXPHOS protein levels were preserved. Molecular dynamics simulations suggested a structural basis for the species difference. GDP formed persistent interactions with F88 in mouse-UCP1, an interaction absent at the corresponding S88 residue in human-UCP1. In-silico substitution of F88 by serine reduced GDP interaction at this site. Thus, human and mouse UCP1 share innate thermogenic activity but differ fundamentally in nucleotide regulation. The F88/S88 difference may contribute to the preferential GDP sensitivity of mouse-UCP1, whereas ATP provides effective nucleotide control of human-UCP1.

biochemistry↗

bioRxiv2024

Structure and Cl-Conductance Properties of the Open State of Human CFTR

The cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel that plays a vital role in water and ion secretion on epithelial surfaces. Loss of function in CFTR causes the life-threatening disease cystic fibrosis (CF). The functionally open state of CFTR has so far eluded detailed structural characterization. Although multiple near-atomic resolution structures of CFTR have been solved under conditions that promote channel opening, they all lack a continuous ion conduction pathway. In recent molecular dynamics (MD) simulations, structural fluctuations of human CFTR in a hydrated lipid bilayer led to the observation of transient Cl- conducting states, but the stability and conduction properties of these putative open states were not established. Here, we conduct massively repeated simulations initiated from these Cl- permeable conformations. Reproducible structural relaxation of the pore leads to a stable open conformation featuring five symmetrically arranged pore-lining helices. Unlike previously reported structures, this novel penta-helical arrangement reproduces experimentally determined properties of the open pore, including a Cl- conductance close to that measured at physiological voltages. Together, our results support the validity of this newly identified pore conformation as a model of the fully open channel. Detailed analysis highlights the role of cationic pore-lining residues in the Cl- permeation mechanism and suggests that the kinks observed in several transmembrane helices play a role in channel gating.

biophysics↗

bioRxiv2022

Structure-based design and characterization of Parkin activating mutations

Human autosomal recessive mutations in the Parkin gene are causal for Parkinsons disease (PD). Parkin encodes a ubiquitin E3 ligase that functions together with the PD associated kinase, PINK1, in a mitochondrial quality control pathway. Structural studies reveal that Parkin exists in an inactive conformation mediated by multiple autoinhibitory domain interfaces. Here we have performed comprehensive mutational analysis of both human and rat Parkin to unbiasedly determine Parkin activating mutations across all major autoinhibitory interfaces. Out of 31 mutations tested, we identify 11 activating mutations clustered near the RING0:RING2 or REP:RING1 interfaces, which reduce the thermal stability of Parkin. Of these, we demonstrate that three mutations, V393D, A401D, and W403A located at the REP:RING1 interface were able to completely rescue a Parkin S65A mutant, defective in mitophagy, in cell-based studies. Overall our data extends previous analysis of Parkin activation mutants and suggests that small molecules that mimic REP:RING1 destabilisation offer therapeutic potential for PD patients harbouring select Parkin mutations. Summary blurbParkin, an E3 ubiquitin ligase involved in Parkinsons disease, is inactive in the basal state and is activated by PINK1 to mediate mitophagy. Here we characterized 31 mutations and discovered three that activate Parkin and rescue loss of PINK1 phosphorylation.

biochemistry↗

bioRxiv2018

Lipid interactions enhance activation and potentiation of cystic fibrosis transmembrane conductance regulator (CFTR)

The recent cryo-electron microscopy structures of phosphorylated, ATP-bound CFTR in detergent micelles failed to reveal an open anion conduction pathway as expected on the basis of previous functional studies in biological membranes. We tested the hypothesis that interaction of CFTR with lipids is important for opening of its channel. Interestingly, molecular dynamics studies revealed that phospholipids associate with regions of CFTR proposed to contribute to its channel activity. More directly, we found that CFTR purified together with associated lipids using the amphipol: A8-35, exhibited higher rates of catalytic activity, channel activation and potentiation using ivacaftor, than did CFTR purified in detergent. Catalytic activity in CFTR detergent micelles was partially rescued by addition of phospholipids plus cholesterol, arguing that these lipids contribute directly to its modulation. In summary, these studies highlight the importance of lipids in regulated CFTR channel activation and potentiation.

biophysics↗