New Insights Into Neuron Resilience Against Alzheimer’s

Recent scientific discoveries indicate that certain brain cells can withstand the harmful effects linked to Alzheimer’s disease and other forms of dementia. Researchers have pinpointed what they’re calling a “cellular hazmat team” that helps maintain the health of neurons.

Neurodegenerative diseases, such as dementia, are marked by the buildup of proteins in the brain that ultimately damage neurons. Tau proteins are often implicated in these processes, but it turns out they aren’t always harmful.

In a healthy state, tau proteins contribute to stabilizing brain structures and supporting nutrient transport. However, when they misfold, they start clumping together. This clumping is associated with the progression of neurodegenerative diseases.

A recent study from UCLA Health and UC San Francisco utilized a CRISPR-based screening approach to investigate tau accumulation within lab-grown neurons sourced from human stem cells. What’s intriguing here is that they focused on neurons possessing a specific mutation related to disease.

“What’s especially noteworthy about this research is that we analyzed human neurons bearing a mutation that actually causes disease,” explains Avi Samelson, an assistant professor at UCLA Health and first author of the study.

These neurons demonstrate natural variations in tau processing, enhancing the credibility of the mechanisms identified as pertinent to human disease.

The mutation involved, MAPT V337M, triggers increased tau protein aggregation, leading to a harmful form known as the “Alzheimer fold.”

In the past, scientists have mapped the human genome to discover factors influencing disease risk but often struggled to understand the molecular mechanisms at play. While differences amongst neurons have been noted, identifying the causative factors has been challenging.

Martin Kampmann, a professor at UC San Francisco and the study’s senior author, states, “This is the first instance where we’ve successfully screened human neurons to find genes that affect their resilience against tau.” Researchers systematically examined nearly every gene in the human genome, knocking down or inactivating around 20,000 individual genes in the cultured human neurons to see how each influenced tau protein clumping. The analysis revealed over a thousand genes implicated in harmful tau accumulation.

Additionally, the study uncovered CRL5SOCS4 as a critical component aiding neuron resistance to toxic tau buildup. This protein complex marks tau proteins for degradation by proteasomes, the cellular “garbage disposal” units.

To verify if their laboratory discoveries align with real-world observations, researchers referenced the Seattle Alzheimer’s Disease Brain Atlas, a resource compiled from brain tissues of deceased Alzheimer’s patients. They found that neurons with higher CRL5SOCS4 expression had a greater chance of survival.

Interestingly, the fragmentation of tau proteins can also be linked to issues in mitochondrial function. When genes involved in mitochondrial activity were silenced, tau protein fragments emerged, which, though small, have characteristics resembling a significant biomarker found in Alzheimer’s patients. These fragments seem to result from oxidative stress, a common issue during energy production that worsens with aging and neurodegeneration.

This makes the tau more prone to clumping due to changes in mitochondrial gene functioning.

The findings shed light on how genetic screening can uncover previously unknown disease mechanisms and suggest some new pathways that manage tau levels, though understanding of these processes may still be incomplete.

Moving forward, clinicians face the challenge of transforming these discoveries into viable treatments. The researchers propose two possible therapeutic strategies: boosting CRL5SOCS4 activity to facilitate the removal of tau proteins before they have a chance to clump, orProtecting proteasomes from oxidative stress to ensure proper processing of tau proteins.

As is often the case with human biology, effective treatments may reflect a combination of natural processes refined over time.

Perhaps, Kampmann muses, future therapies could harness the body’s inherent mechanisms to counteract neurodegeneration.

This research is documented in the journal Cell.