The ototoxic drug cisplatin localises to stress granules altering their dynamics and composition

Abstract

Cisplatin is an effective platinum-based chemotherapeutic with several side effects, including ototoxicity. Cochlear cells have low rates of proliferation yet are highly susceptible to cisplatin. We hypothesized that cisplatin ototoxicity may be caused by cisplatin-protein interactions rather than cisplatin-DNA interactions. Two known cisplatin-binding proteins are involved in the stress granule (SG) response. SGs are a pro-survival mechanism involving formation of transient ribonucleoprotein complexes during stress. We examined the effects of cisplatin on SG dynamics and composition in cell lines derived from the cochlea and retinal pigment epithelium. Cisplatin-induced SGs are significantly diminished in size and quantity compared to arsenite-induced SGs and are persistent after 24 hours recovery. Additionally, cisplatin pre-treated cells were unable to form a typical SG response to subsequent arsenite stress. Cisplatin-induced SGs had significant reductions in the sequestration of eIF4G and proteins RACK1 and DDX3X. Live cell imaging of cisplatin-TR revealed localisation to SGs and retention for at least 24 hours. We show cisplatin-induced SGs have impaired assembly, altered composition and are persistent, providing evidence of an alternate mechanism for cisplatin-induced ototoxicity via an impaired SG response.

Molecular Characteristics of Cisplatin-Induced Ototoxicity and Therapeutic Interventions

“…A recent study [26] revealed that cisplatin localizes to stress granules (SGs). These are non-membranous, irregularly shaped cellular compartments that are transiently assembled in response to various stress stimuli, playing a crucial role in cell survival [27,28].…”

“…SGs are composed of mRNA, RNA-binding proteins, translation factors, and other proteins, and are rapidly disintegrated and cleared upon removal of the stressor [27][28][29]. Martin et al [26] demonstrated that SGs retain cisplatin for at least 24 h, leading to impairments in their assembly, including the reduced sequestration of DEAD-Box Helicase 3 X-Linked (DDX3X) signaling protein essential for inflammasome formation. This leads to alterations Once taken up by the cell, cisplatin undergoes an aquation reaction, creating an activated form that can bind to and damage negatively charged macromolecules within the cell, including DNA, RNA, proteins, and lipids, leading to apoptotic cell death [25].…”

“…SGs are composed of mRNA, RNA-binding proteins, translation factors, and other proteins, and are rapidly disintegrated and cleared upon removal of the stressor [27][28][29]. Martin et al [26] demonstrated that SGs retain cisplatin for at least 24 h, leading to impairments in their assembly, including the reduced sequestration of DEAD-Box Helicase 3 X-Linked (DDX3X) signaling protein essential for inflammasome formation. This leads to alterations in SG dynamics and composition.…”