An emerging role for stress granules in neurodegenerative disease and hearing loss.

Stress granules (SGs) are membrane-less cytosolic assemblies that form in response to stress (e.g., heat, oxidative stress, hypoxia, viral infection and UV). Composed of mRNA, RNA binding proteins and signalling proteins, SGs minimise stress-related damage and promote cell survival. Recent research has shown that the stress granule response is vital to the cochlea's response to stress. However, emerging evidence suggests stress granule dysfunction plays a key role in the pathophysiology of multiple neurodegenerative diseases, several of which present with hearing loss as a symptom. Hearing loss has been identified as the largest potentially modifiable risk factor for dementia. The underlying reason for the link between hearing loss and dementia remains to be established. However, several possible mechanisms have been proposed including a common pathological mechanism. Here we will review the role of SGs in the pathophysiology of neurodegenerative diseases and explore possible links and emerging evidence that they may play an important role in maintenance of hearing and may be a common mechanism underlying age-related hearing loss and dementia.