Biology subjects

Dziurdzik, S. K.

Publications and source records attributed to Dziurdzik, S. K..

4 recordsLinked to original sources

bioRxiv2025

A shared binding interface controls Vps13 organelle-specific targeting independently of its vacuolar protein sorting function

Yeast vacuolar protein sorting 13 (Vps13) is a bridge-like transporter that directs lipid flow between membranes at organelle contact sites. Vps13 targeting relies on organelle-specific adaptors containing proline-X-proline (PxP) motifs, which compete for binding to the Vps13 adaptor-binding (VAB) domain. Though a VAB-PxP interface has been identified for the mitochondrial adaptor Mcp1, whether other adaptors use identical binding mechanisms is unknown. Moreover, not every Vps13 function is connected to a known PxP adaptor, suggesting other adaptors may exist. Here, we validate the significance of the shared VAB-PxP interface by showing that mutations within this region inhibit both adaptor binding and Vps13 membrane targeting in vivo. Using predictive modeling, we demonstrate that while adaptors share a common Vps13-binding interface, slight differences between these interfaces may contribute to preferential binding and adaptor competition. Notably, we find that the VPS pathway functions independently of the PxP motif binding site, and extensive scanning mutagenesis did not reveal a dedicated VPS-specific adaptor interface. Our results indicate the VPS pathway likely employs a non-PxP adaptor mechanism, yet the structural integrity of the VAB domain remains essential for proper pathway function. Significance statementO_LIAdaptor-mediated recruitment of yeast Vps13 to organelles requires a consensus PxP motif. It is unclear if all adaptors bind Vps13 in a similar manner and if all Vps13 functions are dependent on adaptors that contain this motif. C_LIO_LIWe show that Vps13 binds the core PxP motifs from known adaptors through a shared interface, yet this interface is dispensable for Vps13s role in the vacuole protein sorting pathway. C_LIO_LIOur work suggests that Vps13 engages in a wider range of targeting mechanisms than was previously recognized, and that the Vps13 adaptor-binding domain must have a function beyond targeting this consensus motif. C_LI

cell biology↗

bioRxiv2025

Hoi1 targets the yeast BLTP2 protein to ER-PM contact sites to regulate lipid homeostasis

Membrane contact sites between organelles are important for maintaining cellular lipid homeostasis. Members of the recently identified family of bridge-like lipid transfer proteins (BLTPs) span opposing membranes at these contact sites to enable the rapid transfer of bulk lipids between organelles. While the VPS13 and ATG2 family members use organelle-specific adaptors for membrane targeting, the mechanisms that regulate other bridge-like transporters remain unknown. Here, we identify the conserved protein Ybl086c, which we name Hoi1 (Hob interactor 1), as an adaptor that targets the yeast BLTP2-like proteins Fmp27/Hob1 and Hob2 to ER-PM contact sites. Two separate Hoi1 domains interface with alpha-helical projections that decorate the central hydrophobic channel on Fmp27, and loss of these interactions disrupts cellular sterol homeostasis. The mutant phenotypes of BLTP2 and HOI1 orthologs indicate these proteins act in a shared pathway in worms and flies. Together, this suggests that Hoi1-mediated recruitment of BLTP2-like proteins represents an evolutionarily conserved mechanism for regulating lipid transport at membrane contact sites.

cell biology↗

bioRxiv2021

Systematic analysis of membrane contact sites in Saccharomyces cerevisiae uncovers modulators of cellular lipid distribution

Actively maintained close appositions, or contact sites, between organelle membranes, enable the efficient transfer of biomolecules between the various cellular compartments. Several such sites have been described together with their tethering machinery. Despite these advances we are still far from a comprehensive understanding of the function and regulation of most contact sites. To systematically characterize the proteome of contact sites and support the discovery of new tethers and functional molecules, we established a high throughput screening approach in Saccharomyces cerevisiae based on co-localization imaging. We imaged split fluorescence reporters for six different contact sites, two of which have never been studied before, on the background of 1165 strains expressing a mCherry-tagged yeast protein that have a cellular punctate distribution (a hallmark of contact sites). By scoring both co-localization events and effects on reporter size and abundance, we discovered over 100 new potential contact site residents and effectors in yeast. Focusing on several of the newly identified residents, we identified one set of hits as previously unrecognized homologs to Vps13 and Atg2. These proteins share their lipid transport domain, thus expanding this family of lipid transporters. Analysis of another candidate, Ypr097w, which we now call Lec1 (Lipid-droplet Ergosterol Cortex 1), revealed that this previously uncharacterized protein dynamically shifts between lipid droplets and the cell cortex, and plays a role in regulation of ergosterol distribution in the cell.

cell biology↗

bioRxiv2019

A VPS13D spastic ataxia mutation disrupts the conserved adaptor binding site in yeast Vps13

Mutations in each of the four human VPS13 (VPS13A-D) proteins are associated with distinct neurological disorders: chorea-acanthocytosis, Cohen syndrome, early-onset Parkinsons disease and spastic ataxia. Recent evidence suggests that the different VPS13 paralogs transport lipids between organelles at different membrane contact sites. How each VPS13 isoform is targeted to organelles is not known. We have shown that the localization of yeast Vps13 protein to membranes requires a conserved six-repeat region, the Vps13 Adaptor Binding (VAB) domain, which binds to organelle-specific adaptors. Here, we use a systematic mutagenesis strategy to determine the role of each repeat in recognizing each known adaptor. Our results show that mutation of invariant asparagines in repeats 1 and 6 strongly impact the binding all adaptors and block Vps13 membrane recruitment. However, we find that repeats 5 to 6 are sufficient for localization and interaction with adaptors. This supports a model where a single adaptor binding site is found in the last two repeats of the VAB domain, while VAB domain repeat 1 may help maintain domain conformation. Importantly, a disease-causing mutation in VPS13D, which maps to the highly conserved asparagine residue in repeat 6, blocks adaptor binding and Vps13 membrane recruitment when modeled in yeast. Our findings are consistent with a conserved adaptor binding role for the VAB domain and suggests the presence of as-yet-unidentified adaptors in both yeast and humans.

molecular biology↗