Biology subjects

Tapia, K.

Publications and source records attributed to Tapia, K..

3 recordsLinked to original sources

bioRxiv2026

Structure and function of the DFCP1 membrane barrier responsible for ER microdomain organization in lysosome repair

The endoplasmic reticulum (ER) forms specialized microdomains that organize autophagy, lipid droplet formation, and the repair of damaged lysosomes. The PI3P-binding protein DFCP1/ZFYVE1 marks these microdomains, raising the question as to whether and how one protein could define such a subcompartment. Here we determine the structure of full-length human DFCP1 bound to membranes by cryo-electron tomography and single-particle cryo-electron microscopy. DFCP1 assembles into a helical coat, built from tetramers that stack around a constricted membrane tube. Its ATPase domains form the organizing core of the helix, while its ER-targeting domains insert deeply into the outer leaflet, and its FYVE domains grip PI3P. Coarse-grained molecular dynamics simulations show that the coat does not simply follow the curvature of the membrane but acts as a barrier to lipid diffusion, almost completely blocking the movement of its cognate lipid PI3P past the filament and concentrating it beneath the coat. Point mutations that break the assembly, membrane-insertion or PI3P-binding interfaces each impair lysosomal repair in cells, and the assembly is also required for the focal recruitment of the lipid transporter VPS13C. We propose that DFCP1 collars fence off a specialized ER microdomain, so that locally made lipids can reach sites of repair rather than escaping into bulk ER.

cell biology↗

bioRxiv2026

Structural basis for the ATP-dependence of omegasome biogenesis by DFCP1

Autophagosome formation begins at phosphatidylinositol 3-phosphate-enriched endoplasmic reticulum (ER) subdomains termed omegasomes. DFCP1/ZFYVE1 is recruited to omegasomes through its FYVE domains and has recently been shown to function as an ATPase involved in omegasome constriction and autophagosome biogenesis. However, the structural basis of DFCP1 ATPase activity and how nucleotide-dependent conformational states regulate omegasome dynamics remain unknown. Here, we determined the crystal structures of the DFCP1 ATPase domain in complex with either ADP or the non-hydrolyzable ATP analogue, AppNHp at near atomic resolution. We employed structure-guided mutagenesis to define residues required for DFCP1 function in cells. The structures reveal that the active site contains a trans-acting Arg271 finger coordinating the {psi}-phosphate and trans-acting His323 that stacks on the ATP adenine ring. ATP hydrolysis results in a conformational switch in the vicinity of Arg271, while contacts with His323 persist in the presence of ADP. Biochemical analyses of DFCP1 and its mutants show that DFCP1 forms ATP-dependent microdomains on membranes. Disruption of His323 and Arg271 uncouples nucleotide binding from ATP hydrolysis and alters the oligomeric state of the protein. Live-cell imaging of DFCP1 knockout cells reconstituted with wild-type or mutant DFCP1 further demonstrates that these biochemical defects translate into distinct omegasome phenotypes. Together, our data provides a structural-function framework for DFCP1 ATPase activity and reveals how distinct catalytic elements control omegasome dynamics in vivo. We propose that nucleotide-dependent assembly and hydrolysis-driven conformational changes enable DFCP1 to regulate omegasome formation and its progression toward autophagosome closure. Significance StatementDFCP1 organizes the ER subdomains known as omegasomes, which are sites of autophagosome biogenesis. DFCP1 is an ATPase whose catalytic activity is required for function, but the precise role of its ATPase activity is unknown. Crystal structures of the DFCP1 ATPase domain in the presence of a non-hydrolyzable ATP analogue and ADP reveal an Arg finger that operates in trans, such that dimerization is required for ATP hydrolysis, and ATP hydrolysis destabilizes dimers. Dimerization is also promoted by an adenine base-stacking interaction in trans with H323. These residues are important for DFCP1 clustering on membranes and omegasome constriction, clarifying that the role of ATP is to promote the dimerization of the ATPase domain and thereby control the organization of DFCP1 on membranes.

biochemistry↗

bioRxiv2021

Identification of novel human derived influenza viruses in pigs with zoonotic potential.

In 2009, a novel swine influenza A virus (IAV) emerged causing a global pandemic that highlighted the role of swine as a reservoir. To date, there is limited information about swine IAV circulating in Latin America. We identified two swine H1N2 and one divergent swine H3N2 viruses that co-circulated in Chilean swine together with the 2009 H1N1 pandemic strain (A(H1N1)pdm09). Phylogenetic analysis revealed several human-to-swine IAV introductions occurring as early as the mid-1980s, and since 2009, several introductions of the A(H1N1)pdm09 strain. Antigenic cartography confirmed that these viruses were antigenically unique and identified drifted variants within the clusters. Human sera from the Chilean general population showed an age dependent mid to low-level antibody mediated protection against swine H1N2 and A(H1N1)pdm09-like viruses and a poor protection against the swine H3N2 virus, highlighting the zoonotic potential of this strain. Our results underscore the epidemiological importance of studying swine IAV in Latin America for epidemic and pandemic preparedness.

microbiology↗