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Scientists Reverse Alzheimer’s Memory Loss by Repairing Damaged Synapses

Kauwe, Pareja-Navarro et al. identify a KIBRA-dependent mechanism to repair the plasticity at synapses that is dysregulated in neurons underlying the loss of memory in tauopathy. The art depicts the recovery of the functional plasticity at synapses on neurons despite tau-induced toxicity in the brain. Credit: Larissa Brown

A groundbreaking study presents a novel Alzheimer’sAlzheimer's disease is a disease that attacks the brain, causing a decline in mental ability that worsens over time. It is the most common form of dementia and accounts for 60 to 80 percent of dementia cases. There is no current cure for Alzheimer's disease, but there are medications that can help ease the symptoms.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Alzheimer’s treatment strategy focusing on memory restoration through the repair of damaged synapses, leveraging the critical role of the KIBRA protein. This approach shows promise in reversing memory loss without directly addressing the accumulation of toxic proteins.

While newly approved drugs for Alzheimer’s show some promise for slowing the memory-robbing disease, the current treatments fall far short of being effective at regaining memory. What is needed are more treatment options targeted to restore memory, said Buck Assistant Professor Tara Tracy, PhD, the senior author of a study that proposes an alternate strategy for reversing the memory problems that accompany Alzheimer’s disease and related dementias.

Exploring New Avenues for Alzheimer’s Treatment

Since most current research on potential treatments for Alzheimer’s focuses on reducing the toxic proteins, such as tau and amyloid beta, that accumulate in the brain as the disease progresses, the team veered away from this route to explore an alternative. “Rather than trying to reduce toxic proteins in the brain, we are trying to reverse the damage caused by Alzheimer’s disease to restore memory,” said Tracy. The findings appear in the February 1 issue of The Journal of Clinical Investigation.

The work hinges on a protein called KIBRA, named because it is found in the kidney and the brain. In the brain, it is primarily localized at the synapses, which are the connections between neurons that allow memories to be formed and recalled. Research has shown that KIBRA is required for synapses to form memories, and Tracy’s team has found that brains with Alzheimer’s disease are deficient in KIBRA.

The Role of KIBRA in Memory Restoration

“We wondered how the lower levels of KIBRA affected signaling at the synapseA synapse is a specialized junction between nerve cells that allows for the transfer of electrical or chemical signals, through the release of neurotransmitters by the presynaptic neuron and the binding of receptors on the postsynaptic neuron. It plays a key role in communication between neurons and in various physiological processes including perception, movement, and memory.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>synapse, and whether understanding that mechanism better could yield some insight into how to repair the synapses damaged during the course of Alzheimer’s disease,” said Buck Staff Scientist ​​Grant Kauwe, PhD, co-first author of the study. “What we identified is a mechanism that could be targeted to repair synaptic function, and we are now trying to develop a therapy based on this work.”

The team first measured the levels of KIBRA in the cerebrospinal fluid of humans. They found that higher levels of KIBRA in the cerebrospinal fluid, but lower levels in the brain, corresponded to the severity of dementia.

“We also found this amazing correlation between increased tau levels and increased KIBRA levels in the cerebrospinal fluid,” said Tracy. “It was very surprising how strong the relationship was, which really points to the role of KIBRA being affected by tau in the brain.” The team is exploring this phenomenon further, in hopes that KIBRA could be used as a biomarker of synaptic dysfunction and cognitive decline that could be useful for diagnosis, treatment planning, and tracking disease progression and response to therapy.

Promising Results from KIBRA Research

To figure out how KIBRA affects synapses, the team created a shortened functional version of the KIBRA protein. In laboratory mice that have a condition mimicking human Alzheimer’s disease, they found that this protein can reverse the memory impairment associated with this type of dementia. They found that KIBRA rescues mechanisms that promote the resilience of synapses.

“Interestingly, KIBRA restored synaptic function and memory in mice, despite not fixing the problem of toxic tau protein accumulation,” said Kristeen Pareja-Navarro, co-first author of the study. “Our work supports the possibility that KIBRA could be used as a therapy to improve memory after the onset of memory loss, even though the toxic protein that caused the damage remains.”

Along with other treatments that already exist or will come in the future, a KIBRA therapy to repair synapses could be a valuable addition. “Reducing toxic proteins is of course important, but repairing synapses and improving their function is another critical factor that could help,” said Tracy. “That’s how I see this making the biggest impact in the future.”

Reference: “KIBRA repairs synaptic plasticity and promotes resilience to tauopathy-related memory loss” by Grant Kauwe, Kristeen A. Pareja-Navarro, Lei Yao, Jackson H. Chen, Ivy Wong, Rowan Saloner, Helen Cifuentes, Alissa L. Nana, Samah Shah, Yaqiao Li, David Le, Salvatore Spina, Lea T. Grinberg, William W. Seeley, Joel H. Kramer, Todd C. Sacktor, Birgit Schilling, Li Gan, Kaitlin B. Casaletto and Tara E. Tracy, 1 February 2024, The Journal of Clinical Investigation.
DOI: 10.1172/JCI169064

Other Buck researchers involved in the study are: Lei Yao, Jackson H. Chen, Ivy Wong, Helen Cifuentes, Samah Shah, and Birgit Schilling

Source: SciTechDaily