bims-hypusi 2023-12-10 papers

Issue of 2023–12–10
two papers selected by
Sebastian J. Hofer, University of Graz

Diabetes. 2023 Dec 06. pii: db230148. [Epub ahead of print]

A translational regulatory mechanism mediated by hypusinated eukaryotic initiation factor 5A facilitates beta cell identity and function.

Craig T Connors, Catharina B P Villaca, Emily K Anderson-Baucum, Spencer R Rosario, Caleb D Rutan, Paul J Childress, Leah R Padgett, Morgan A Robertson, Teresa L Mastracci.

As professional secretory cells, beta cells require adaptable mRNA translation to facilitate a rapid synthesis of proteins, including insulin, in response to changing metabolic cues. Specialized mRNA translation programs are essential drivers of cellular development and differentiation. However, in the pancreatic beta cell, the majority of factors identified to promote growth and development function primarily at the level of transcription. Therefore, despite its importance, the regulatory role of mRNA translation in the formation and maintenance of functional beta cells is not well defined. In this study, we have identified a translational regulatory mechanism mediated by the specialized mRNA translation factor eukaryotic initiation factor 5A (eIF5A), which facilitates the maintenance of beta cell identity and function. The mRNA translation function of eIF5A is only active when it is post-translationally modified ("hypusinated") by the enzyme deoxyhypusine synthase (DHPS). We have discovered that the absence of beta cell DHPS in mice reduces the synthesis of proteins critical to beta cell identity and function at the stage of beta cell maturation, leading to a rapid and reproducible onset of diabetes. Therefore, our work has revealed a gatekeeper of specialized mRNA translation that permits the beta cell, a metabolically responsive secretory cell, to maintain the integrity of protein synthesis necessary during times of induced or increased demand.

DOI: https://doi.org/10.2337/db23-0148

Discov Med. 2023 Dec;35(179): 1167-1176

EIF5A2 Promotes Doxorubicin Resistance in Bladder Cancer Cells through the TGF-β Signaling Pathway.

Jinsong Yang, Xue Jiang, Ying Chen, Lisong Teng.

BACKGROUND: Doxorubicin (DOX) is a commonly used chemotherapeutic agent, but bladder cancer (BC) patients often develop resistance that limits therapeutic efficacy. Recent research has demonstrated a link between medication resistance and the expression of eukaryotic translation initiation factor 5A2 (EIF5A2) in tumors. This study aimed to investigate whether EIF5A2 affects the resistance of BC cells to doxorubicin through the transforming growth factor (TGF)-β signaling pathway.
METHODS: Doxorubicin-resistant cells in BC (T24/DOX and 5637/DOX) were constructed, then cell viability was detected by cell counting kit-8 (CCK-8); EIF5A2 mRNA expression was detected using quantitative real-time PCR (qRT-PCR); cell proliferation was detected using clone formation; apoptosis was detected by flow cytometry; and finally, proteins related to the TGF-β signaling pathway (EIF5A2, TGF-β1, p-small mothers against decapentaplegic 2 (Smad2)/Smad2, p-Smad3/Smad3) were detected using western blot.
RESULTS: EIF5A2 was up-regulated in DOX-resistant BC cells, and DOX intervention promoted proliferation and inhibited apoptosis in DOX-resistant BC cells. si-EIF5A2 reversed the above effects. EIF5A2 resulted in DOX resistance by activating the TGF-β pathway, and the TGF-β activator SRI-011381 reversed the inhibitory effect of si-EIF5A2 on DOX resistance.
CONCLUSIONS: EIF5A2 promotes DOX resistance in BC cells through the TGF-β signaling pathway, and EIF5A2 may be a potential counter-resistance therapeutic strategy in BC chemotherapy.

Keywords: EIF5A2; TGF-β; bladder cancer; doxorubicin

DOI: https://doi.org/10.24976/Discov.Med.202335179.113