Biology subjects

Arnold, M. E.

Publications and source records attributed to Arnold, M. E..

3 recordsLinked to original sources

bioRxiv2025

Identification and Validation of an Interaction between the E3 Ubiquitin Ligase WWP1 and the Transcriptional Co-Activator WBP2 in the Human Heart

Impaired proteostasis is one of the cellular hallmarks of aging, and the ubiquitin-proteosome system is a fundamental driver of proteostasis. As an E3 ubiquitin ligase, WW-domain containing protein 1 (WWP1) expression and activity are tightly regulated in cells, while its deregulation has been described in cancer, in neurodegenerative diseases, and in heart failure. However, the protein-protein interaction network of WWP1 is understudied, particularly in the heart. Here, we conducted a yeast-two hybrid (Y2H) screen of a human heart library and identified 21 putative WWP1 interactors, including 12 whose expression and potential function in the heart were previously unappreciated. Chief among these was WBP2 (WW domain binding protein 2), an oncogenic transcriptional co-activator. Utilizing immunofluorescence, it was confirmed that endogenous WWP1 co-localizes with WBP2 in human heart tissue, and, using the Y2H system, we showed that this interaction is dependent upon the associations between WW domains 1 and 3 from WWP1 and PY domains 2 and 3 of WBP2. In total, these data serve as a launching pad to identify broader protein networks regulated by WWP1 and the regions of interaction which might be targetable to reduce hallmarks of cellular aging.

molecular biology↗

bioRxiv2024

A negative feedback loop between small GTPase Rap1 and mammalian tumor suppressor homolog KrsB regulates cell-substrate adhesion in Dictyostelium

Cell adhesion to the substrate influences a variety of cell behaviors and its proper regulation is essential for migration, although details of the molecular pathways regulating cell adhesion during migration are lacking. Rap1 is a small GTPase that regulates adhesion in mammalian cells, as well as in Dictyostelium discoideum social amoeba, which is an established model for studying directed cell migration. In Dictyostelium, Rap1 controls adhesion via its effects on adhesion mediator talin and Ser/Thr kinase Phg2, which inhibits myosin II function. Kinase responsive to stress B (KrsB), a homolog of mammalian tumor suppressor MST1/2 and Drosophila Hippo, also regulates cell adhesion and migration, although the molecular mechanism of KrsB action is not understood. Since KrsB has been shown to interact with active Rap1 by mass spectroscopy, we investigated the genetic interaction between Rap1 and KrsB. Cells lacking KrsB have increased adhesion to the substrate, which leads to reduced movement. Expression of constitutively active Rap1 G12V increased cell spreading and adhesion even in the absence of KrsB, suggesting that Rap1 does not require KrsB to mediate cell adhesion. In contrast, dominant negative Rap1 S17N completely reversed the over-adhesive phenotype of KrsB-null cells and impaired KrsB phosphorylation, suggesting that KrsB activation and function in adhesion requires Rap1. Even though Rap1 did not require KrsB for its function in adhesion, KrsB negatively regulates Rap1 function as seen by increased cortical localization of Rap1 in KrsB-null cells. Consistent with this, chemoattractant-induced activation of downstream effectors of Rap1, TalB and Phg2, was increased in the absence of KrsB. Taken together, these findings suggest that Rap1 leads to activation of KrsB, which inhibits Rap1 and its downstream targets, shutting off adhesion. The existence of a negative feedback loop between Rap1 and KrsB may contribute to the dynamic regulation of cell adhesion that is necessary for rapid amoeboid-type migration.

cell biology↗

bioRxiv2019

Single-cell profiles of retinal neurons differing in resilience to injury reveal neuroprotective genes

Neuronal types in the central nervous system differ dramatically in their resilience to injury or insults. Here we studied the selective resilience of mouse retinal ganglion cells (RGCs) following optic nerve crush (ONC), which severs their axons and leads to death of ~80% of RGCs within 2 weeks. To identify expression programs associated with differential resilience, we first used single-cell RNA-seq (scRNA-seq) to generate a comprehensive molecular atlas of 46 RGC types in adult retina. We then tracked their survival after ONC, characterized transcriptomic, physiological, and morphological changes that preceded degeneration, and identified genes selectively expressed by each type. Finally, using loss- and gain-of-function assays in vivo, we showed that manipulating some of these genes improved neuronal survival and axon regeneration following ONC. This study provides a systematic framework for parsing type-specific responses to injury, and demonstrates that differential gene expression can be used to reveal molecular targets for intervention.

neuroscience↗