GADD45GIP1 promotes osteosarcoma progression by modulating RPL35 ubiquitination and alleviating endoplasmic reticulum stress via the PERK/eIF2α pathway.

Osteosarcoma, a common and aggressive bone tumor found in adolescents and children, is associated with a poor prognosis. The investigation of new molecular mechanisms is deemed vital for the development of innovative treatments. Transcriptomic survival analysis and single-cell RNA sequencing have identified seven highly expressed genes, including GADD45G interacting protein 1 (GADD45GIP1), that are linked to poor prognosis in patients with osteosarcoma. Tissue arrays, comprising 41 normal and 67 tumor cases, have further confirmed the high expression of GADD45GIP1 in osteosarcoma. Functional tests have demonstrated that the silencing of GADD45GIP1 significantly reduces the migration and proliferation of osteosarcoma cells in vitro and in vivo, while its overexpression has the opposite effect. Mechanistic studies have revealed 263 proteins that potentially interact with GADD45GIP1, identified through immunoprecipitation (IP) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), with RPL35 ranking second among them. Cellular interference with RPL35 has been shown to activate the PERK-eIF2α pathway, increase endoplasmic reticulum (ER) stress, and affect the biological behavior of tumor cells. Additionally, the knockdown of GADD45GIP1 has led to a decrease in RPL35 protein stability and elevated polyubiquitination. Notably, the overexpression of RPL35 has counteracted the decrease in cell vitality induced by GADD45GIP1 knockdown. Thus, the high expression of GADD45GIP1 in osteosarcoma has been shown to inhibit the ubiquitin-mediated degradation of RPL35 and induce ER stress through the activation of the PERK-eIF2α pathway, thereby promoting the progression of osteosarcoma. This indicates that GADD45GIP1 serves as a key driver in the development of osteosarcoma and is a potential target for the prevention and therapy of osteosarcoma.