HSPA9 (Mortalin, GRP75) is a heat shock protein involved in cell proliferation, stress response and mitochondria maintenance. HSPA9 is of interest in neurodegenerative diseases including Alzheimer’s and Parkinson’s disease; it may have protective chaperone functions in the brain that help degrade and maintain lowered levels of aggregated or improperly folded proteins. In immunohistochemistry, HSPA9 has granular cytoplasmic positivity in all tissues. References: Front Endocrinol (Lausanne). 2018; 9: 196, PMID: 29755410; J Alzheimers Dis. 2014;38(1):165-70. doi: 10.3233/JAD-130428, PMID: 23948933; J Alzheimers Dis. 2014;38(1):165-70, PMID: 23948933