Biology subjects

Ptak, C.

Publications and source records attributed to Ptak, C..

4 recordsLinked to original sources

bioRxiv2026

Survey of nucleotide-specific Rab GTPase interactions reveals multiple Rab effectors

Rab GTPases control myriad molecular functions by acting as a nucleotide-dependent switch for protein-protein interactions localized in discrete subcellular regions. Finding additional molecular roles for Rab GTPases depends on expanding the identification of their nucleotide-dependent interactions. Here we compare the interactome of Rab GTPases using a comprehensive large-scale yeast 2-hybrid approach powered by quantitative high-throughput sequencing, which was used to find interactions of the major mammalian Rab isoforms locked in a GDP or GTP conformation. These data showed an expanded set of interactions specific for GTP-bound Rab proteins, which many know Rab effectors shown capable of binding a wider repertoire of partners than previously appreciated. We also identified the RGS domain of Snx13 and Snx14 as a new Rab GTPase-binding domain that may bridge these ER-localized proteins with Rab5 and Rab11 endosomal compartments, respectively.

cell biology↗

bioRxiv2023

PMP22 associates with MPZ via their transmembrane domains and disrupting this interaction causes a loss-of-function phenotype similar to hereditary neuropathy associated with liability to pressure palsies (HNPP).

PMP22 and MPZ are abundant myelin membrane proteins in Schwann cells. The MPZ adhesion protein holds myelin wraps together across the intraperiod line. PMP22 is a tetraspan protein belonging to the Claudin superfamily. Loss of either MPZ or PMP22 causes severe demyelinating Charcot-Marie-Tooth (CMT) peripheral neuropathy, and duplication of PMP22 causes the most common form of CMT, CMT1A. Yet, the molecular functions provided by PMP22 and how its alteration causes CMT are unknown. Here we find MPZ and PMP22 form a specific complex through interfaces within their transmembrane domains. We also find that the PMP22 A67T patient variant that causes a loss-of-function (Hereditary Neuropathy with Pressure Palsies) phenotype maps to this interface, and blocks MPZ association without affecting localization to the plasma membrane or interactions with other proteins. These data define the molecular basis for the MPZ~PMP22 interaction and indicate this complex fulfills an important function in myelinating cells.

neuroscience↗

bioRxiv2022

Characterization of the Tau Interactome in Human Brain Reveals Isoform-Dependent Interaction with 14-3-3 Family Proteins

Tau phosphorylation and aggregation is the final common pathway for neuronal toxicity across multiple neurodegenerative diseases including Alzheimer disease, progressive supranuclear palsy, and corticobasal degeneration. We have previously shown that the fetal brain expresses high levels of phosphorylated tau, and even tau aggregates, without apparent toxic effects. The mechanisms for this remarkable resilience, however, remain unclear. In order to identify potential mediators of this resilience, we used bead-linked total tau immunoprecipitation in human fetal, adult, and Alzheimer disease brains. We then used heterologous transfection in HEK 293T cells followed by coimmunoprecipitation, mass photometry, and nuclear magnetic resonance (NMR) to further characterize the interaction of tau with one of our top hits, 14-3-3-{beta}. We found significant differences between the tau interactome in fetal and AD brain, with little difference between adult and AD. There were significant differences in tau interaction with 14-3-3 family proteins between fetal and AD brain. We then determined that the 14-3-3 isoform with the highest difference, 14-3-3-{beta}, preferentially interacts with 4R tau in vitro, forming a complex consisting of two 14-3-3-{beta}, and one tau molecule. NMR studies using 15N-labeled phosphorylated tau showed that the binding site for 14-3-3 was in the microtubule binding region of tau, which is truncated in 3R tau through the exclusion of exon 10. Our findings suggest that there are marked differences between the phospho-tau interactome in fetal and Alzheimer disease brain, including differences in interaction with the critical 14-3-3 family of protein chaperones, which may explain, in part, the resilience of fetal brain to tau toxicity.

neuroscience↗

bioRxiv2021

Phosphorylation-dependent mitotic SUMOylation drives nuclear envelope-chromatin interactions

In eukaryotes, chromatin binding to the inner nuclear membrane (INM) and nuclear pore complexes (NPCs) contributes to spatial organization of the genome and epigenetic programs important for gene expression. In mitosis, chromatin-nuclear envelope (NE) interactions are lost and then formed again as sister chromosomes segregate to post-mitotic nuclei. Investigating these processes in S. cerevisiae, we identified temporally and spatially controlled phosphorylation-dependent SUMOylation events that positively regulate post-metaphase chromatin association with the NE. Our work establishes a phosphorylation-mediated targeting mechanism of the SUMO ligase Siz2 to the INM during anaphase, where Siz2 binds to and SUMOylates the VAP protein Scs2. The recruitment of Siz2 through Scs2 is further responsible for a wave of SUMOylation along the INM that supports the assembly and anchorage of subtelomeric chromatin at the INM and localization of an active gene (INO1) to NPCs during the later stages of mitosis and into G1-phase.

cell biology↗