Sophia Fisher
Pronouns: she/ her
Research Mentor(s): Qing Li
Research Mentor School/College/Department: Medicine Division of Hematology & Oncology / Medicine
Program: UROPF
Session: Session 4 (1:40pm – 2:30pm)
Authors: Erin Kropp, Sophia Fisher, Qing Li
Abstract
Hematopoietic stem cells (HSC) are multipotent cells that have the ability to self-renew and differentiate into all types of blood cells, including, red and white blood cells, and platelets throughout a lifetime. These properties are also the basis for stem cell derived therapies including autologous gene therapy and allogeneic transplant, which is the only curative treatment for many hematologic malignancies. While these therapies hold curative potential for many diseases, they can be limited by low number HSC or donor availability for non-white ethnicities. Ex vivo expansion of HSC provides a potential therapeutic solution, however, Historically, expansion of HSC in culture has been limited by stem cell exhaustion and decreased functional capacity. Recent studies suggest that dysregulated protein homeostasis is associated with loss of HSC function and depletion in culture. We have found endoplasmic reticulum associated degradation (ERAD) decreases with HSC culture. ERAD is a multiprotein complex that degrades misfolded proteins in the ER and regulates secreted and cell surface proteins. Steady state HSCs are highly reliant on ERAD and loss of ERAD activity is associated with depletion of the HSC pool. In HSCs, loss of ERAD activity leads to dysregulation of ERAD substrates such as Rheb and the thrombopoietic receptor, MPL, which causes HSC proliferation and loss of self renewal. Our central hypothesis is the loss of ERAD activity is associated with a loss of HSCs in ex vivo culture and restoring ERAD function will improve HSC frequency and function in culture. To overcome this, we developed a high throughput screen to identify novel regulators of ERAD activity. A preliminary screen using the FDA repurposing library has identified two novel inhibitors of ERAD activity and four promoters of ERAD activity. . The four promoters of ERAD activity belong to a class of compounds, HSP90 inhibitors. In our proposed studies, we will confirm that these molecules modulate ERAD activity by measuring steady state degradation of ERAD substrates IRE1a and Rheb by immunoblot in vitro cell lines 293T and K562 treated with our ERAD modulators.. AWe expect that activators will decrease ERAD substrate levels and inhibitors will increase their levels relative to control. In the future, we will then test their ability to maintain HSC in culture and measure frequency by flow cytometry. We expect that promoting ERAD activity will enrich HSC in ex vivo expansion.
