Biology subjects

Hersh, L. B.

Publications and source records attributed to Hersh, L. B..

4 recordsLinked to original sources

bioRxiv2026

Insulin-degrading enzyme activity is modulated by interaction with pyrroline-5-carboxylate reductase 1

Insulin-degrading enzyme (IDE, insulysin, insulinase) is a peptidase that hydrolyzes a number of bioactive peptides including insulin and the amyloid beta peptide, making it a promising therapeutic target for diabetes and Alzheimers disease. Aspects of its physiological role are still controversial, however. In an attempt to further define IDEs role in cells, we used co-immunoprecipitation experiments to identify potential IDE interacting proteins. The enzyme pyrroline-5-carboxylate reductase 1 (PYCR1) was found associated with IDE in three different cell lines, and the two proteins colocalize in HeLa cells. Purified PYCR1 activates IDE toward small peptide substrates, suggesting a modulatory role for the interaction in vivo. Modeling suggests that the unstructured N-terminal region of PYCR1 inserts into allosteric sites of IDE, contributing to the observed activation. Deleting this sequence alters, but does eliminate, the interaction between PYCR1 and IDE. Since pyrroline-5-carboxylate reductase 1 is a mitochondrial protein, we posit that their interaction could regulate a previously described mitochondrial pool of IDE, which may serve to degrade mitochondrial targeting sequences or amyloid beta peptide that localizes to that organelle.

biochemistry↗

bioRxiv2023

Structure of puromycin-sensitive aminopeptidase and polyglutamine binding

Puromycin-sensitive aminopeptidase (E.C. 3.4.11.14, UniProt P55786), a zinc metallopeptidase belonging to the M1 family, degrades a number of bioactive peptides as well as peptides released from the proteasome, including polyglutamine. We report the crystal structure of PSA at 2.3 A'. Overall, the enzyme adopts a V-shaped architecture with four domains characteristic of the M1 family aminopeptidases, but it is in a less compact conformation compared to most M1 enzymes of known structure. A microtubule binding sequence is present in a C-terminal HEAT repeat domain of the enzyme in a position where it might serve to mediate interaction with tubulin. In the catalytic metallopeptidase domain, an elongated active site groove lined with aromatic and hydrophobic residues and a large S1 subsite may play a role in broad substrate recognition. The structure with bound polyglutamine shows a possible interacting mode of this peptide, which is supported by mutation.

biochemistry↗

bioRxiv2021

Toxoplasma gondii Toxolysin 4 contributes to efficient parasite egress from host cells

Egress from host cells is an essential step in the lytic cycle of T. gondii and other apicomplexan parasites; however, only a few parasite secretory proteins are known to affect this process. The putative metalloproteinase Toxolysin 4 (TLN4) was previously shown to be an extensively processed microneme protein, but further characterization was impeded by the inability to genetically ablate TLN4. Herein we show that TLN4 has the structural properties of an M16 family metalloproteinase, that it possesses proteolytic activity on a model substrate, and that genetic disruption of TLN4 reduces the efficiency of egress from host cells. Complementation of the knockout strain with the TLN4 coding sequence significantly restored egress competency, affirming that the phenotype of the {Delta}tln4 parasite was due to the absence of TLN4. This work identifies TLN4 as the first metalloproteinase and the second microneme protein to function in T. gondii egress. The study also lays a foundation for future mechanistic studies defining the precise role of TLN4 in parasite exit from host cells. IMPORTANCEAfter replicating within infected host cells, the single celled parasite Toxoplasma gondii must rupture out of such cells in a process termed egress. Although it is known that T. gondii egress is an active event that involves disruption of host-derived membranes surrounding the parasite, very few proteins that are released by the parasite are known to facilitate egress. In this study we identify a parasite secretory protease that is necessary for efficient and timely egress, thus laying the foundation for understanding precisely how this protease facilitates T. gondii exit from host cells.

microbiology↗

bioRxiv2020

Development and validation of nanobodies specific to the oncogenic phosphatase Protein Tyrosine Phosphatase 4A3 (PTP4A3 or PRL-3)

Phosphatase of Regenerating Liver-3 (PRL-3) is associated with cancer progression and metastasis in various solid tumors and leukemias. The mechanisms that drive PRL-3s oncogenic functions are not well understood, in part due to a lack of research tools available to study this protein. In particular, small molecules do not exhibit binding specificity for PRL-3 over highly homologous family members PRL-1 and PRL-2, and antibodies directed against PRL-3 are limited by assay type. We have begun to address these issues by developing alpaca-derived single domain antibodies, or nanobodies, targeting PRL-3 with a KD of 30-300 nM and no activity towards PRL-1 and PRL-2. Hydrogen deuterium exchange mass spectrometry (HDX-MS) and co-immunoprecipitation with a known PRL-3 substrate showed the nanobodies bind PRL-3 outside of the active site, meaning they can be used to study PRL-3 interaction with binding partners. The nanobodies were also specific to PRL-3 over other PRLs in immunoprecipitation and immunofluorescence experiments in human cancer cells that overexpressed the PRL family. We found that N-terminal tags on PRL-3, such as GFP and FLAG, changed PRL-3 localization compared to untagged protein, indicating that the nanobodies may provide new insights into PRL-3 trafficking and function. The anti-PRL-3 nanobodies represent an important expansion of the research tools available to study PRL-3 function and can be used to define the role of PRL-3 in cancer progression.

biochemistry↗