CellularFunctions of HsClpXP. The primary function of HsClpXP is tofacilitate the rapid turnover of specific substrate proteins thatare misfolded, thereby preventing their accumulation asprotein aggregates that cause impairment of normal cellularfunction. Indeed, the level of HsClpXP expression is known toincrease during a mitochondrial unfolded protein response(UPRmt) in response to the accumulation of misfoldedmitochondrial proteins,14 mitochondrial frataxin deficiency,15and respiratory deficiency caused by mutations in mitochondrialDNA (mtDNA)