Poster abstracts
Poster number 136 submitted by Kanishk Neerumalla
Yeast and HeLa models of Shwachman-Diamond Syndrome deficiency reveal TP53-independent activation of p38/Hog1 and integrated stress response signaling
Kanishk Neerumalla (1Departments of Pediatrics and Heart, Blood, Kidney Research, Cleveland Clinic, Cleveland, OH, 2Case Western Reserve University College of Arts and Sciences), Neha Prasad (1Departments of Pediatrics and Heart, Blood, Kidney Research, Cleveland Clinic, Cleveland, OH), Noah Saito (1Departments of Pediatrics and Heart, Blood, Kidney Research, Cleveland Clinic, Cleveland, OH, 2Case Western Reserve University College of Arts and Sciences), Xin Chen (1Departments of Pediatrics and Heart, Blood, Kidney Research, Cleveland Clinic, Cleveland, OH), Samay Shah (1Departments of Pediatrics and Heart, Blood, Kidney Research, Cleveland Clinic, Cleveland, OH, 2Case Western Reserve University College of Arts and Sciences), Seth J Corey (1Departments of Pediatrics and Heart, Blood, Kidney Research, Cleveland Clinic, Cleveland, OH)
Abstract:
Shwachman-Diamond syndrome (SDS) is an inherited ribosomopathy. About 90% of patients harbor biallelic SBDS mutations. Eukaryotic initiation factor 6 (eIF6) blocks the surface where 60S would meet 40S, keeping it inactive. SBDS works with the GTPase EFL1 to release eIF6, allowing 60S and 40S to form the mature 80S ribosome. Loss of SBDS impairs this step. The resulting shortage of translating ribosomes produces tissue-specific defects. Dogma holds TP53 mediates this phenotype, yet crossing TP53 loss-of-function with sbds-/- zebrafish rescued neither neutropenia nor lethality. Yeast lacks TP53, yet loss of the SBDS ortholog SDO1 markedly reduces growth. Therefore, we hypothesize that TP53-independent mechanisms exist. Cells answer ribosomal stress by two distinct pathways. The first is a ribotoxic stress response involving p38 MAP kinase, whose yeast ortholog is Hog1. Once phosphorylated, Hog1 enters the nucleus and induces targets such as GPD1. The second, the integrated stress response (ISR), acts on translation rather than transcription. GCN2 phosphorylates eIF2α, lowering global translation while raising select transcription factors, GCN4 in yeast and ATF4 and CHOP in humans. sdo1Δ cells doubled in ~9 h versus 1.5 h in wild type (WT). Under osmotic stress, sdo1Δ showed elevated Hog1 phosphorylation and GPD1 induction over WT. Under oxidative stress, sdo1Δ raised GCN2, phospho-eIF2α, and GCN4 above WT. Glucose deprivation likewise raised phospho-eIF2α. Overexpressing the Hog1 phosphatase Ptc1 reversed this and restored growth. We next studied SBDS-null HeLa cells, which express TP53. Untreated cells showed elevated CHOP and more stress granules than WT, indicating basal ISR activation. After arsenite, an oxidative stressor, this was reversed, with WT forming more granules. ATF4 and phospho-eIF2α rose in both genotypes. SBDS loss therefore engages p38/Hog1 and the ISR via TP53-independent routes in yeast and human cells, suggesting druggable mechanisms of chronic stress signaling in SDS.
References:
Kawashima N, Prasad N, Tedeschi F, Mehta HM, Saito N, Jones C, Chen X, Hristodor AM, Zhou G, Luna J, Cipolli M, Bezzerri V, Corey SJ. Hog1/p38 and ZAKα drive Shwachman-Diamond syndrome and provide targets to improve cell growth. bioRxiv. 2026. doi:10.64898/2026.02.05.703873. Preprint.
Keywords: Shwachman-Diamond syndrome, Ribosomopathy, Integrated Stress Response