In a healthy brain, the multistep waste clearance process known as autophagy routinely removes and degrades damaged cell components – including malformed proteins like tau and toxic mitochondria. This cellular debris would otherwise pile up like uncollected trash to drive the death of brain cells (neurons), ultimately destroying cognitive abilities like thinking, remembering and reasoning in patients with Alzheimer’s and certain other neurodegenerative diseases.

The protein p62, a selective autophagy cargo receptor, plays a major role in clearing misfolded tau proteins and dysfunctional mitochondria, the energy powerhouse in all cells including neurons. Through autophagy (meaning “self-eating” in Greek) old or broken cellular material is ultimately digested and recycled in lysosomes, membrane-bound structures that work like mini-waste management plants.

Now, neuroscientists at the University of South Florida Health (USF Health) Byrd Alzheimer’s Center report for the first time that the protein phosphatase Slingshot-1, or SSH1 for short, disrupts p62’s ability to function as an efficient “garbage collector” and thereby impairs the disposal of both damaged tau and mitochondria leaking toxins. In a preclinical study, the researchers showed that SSH1’s influence in halting p62-mediated protective clearance of tau was separate from SSH1’s role in activating cofilin, an enzyme that plays an essential part in worsening tau pathology.

Their findings were published Oct. 12 in Autophagy.