Brain Protein ATIP Linked to Lower Amyloid Burden in Alzheimer’s Disease

A protein once largely overlooked by neuroscientists may hold important clues to the biology of Alzheimer’s disease. In a study published in Aging Cell, researchers report that higher levels of the angiotensin II type 2 receptor-interacting protein, known as ATIP, in the postmortem frontal cortex of older adults with Alzheimer’s disease are associated with a substantially lower burden of amyloid-beta, the sticky protein fragment that accumulates into the hallmark plaques of the disease. The finding marks the first time ATIP levels have been directly quantified in human Alzheimer’s disease brain tissue, and it points to a potentially underexplored arm of the brain’s renin-angiotensin system as a player in neurodegeneration.

Alzheimer’s disease affects an estimated 7.2 million Americans aged 65 and older, a figure expected to climb to 13.8 million by 2060. Despite decades of research into amyloid accumulation, tau pathology, oxidative stress, mitochondrial dysfunction, and chronic inflammation, the aging-related mechanisms that drive the disease remain incompletely understood. The new study homes in on the brain renin-angiotensin system, a hormonal signaling network best known for blood pressure regulation but increasingly implicated in cognition, inflammation, and vascular health within the brain.

Within this system, angiotensin II acts on two principal receptor subtypes: the type 1 receptor and the type 2 receptor. Hyperactivation of the type 1 receptor has been linked to inflammation, oxidative damage, mitochondrial decline, and impaired autophagy in the brain. The type 2 receptor, by contrast, belongs to the protective arm of the system, promoting nitric oxide release, vasodilation, neurite outgrowth, and anti-inflammatory effects. Animal studies have shown that activating the type 2 receptor reduces cortical and hippocampal amyloid plaques and protects against cognitive impairment, but the downstream signaling pathways responsible remained murky.

That is where ATIP enters the picture. ATIP proteins, encoded by the MTUS1 gene through alternative splicing, bind directly to the type 2 receptor and help localize it to the cell membrane, mediating some of its functions. Expression of ATIP variants is highest in the central nervous system, and prior work has shown that upon receptor activation, ATIP forms a complex with the tyrosine phosphatase SHP-1 that translocates to the nucleus and triggers neural differentiation and protection. Given these properties, the research team hypothesized that ATIP might be a key factor connecting the protective angiotensin axis to amyloid pathology.

To test the idea, the investigators analyzed postmortem frontal cortex samples from the Rush Memory and Aging Project, an ongoing cohort study in which participants agree to annual clinical evaluations and brain donation. The sample comprised 60 older adults diagnosed with Alzheimer’s disease, evenly split between those who had used angiotensin receptor blockers, a class of blood pressure drugs that selectively blocks the type 1 receptor, and those who had not. Participants using ACE inhibitors were excluded to avoid confounding effects on renin-angiotensin signaling, and the two groups were matched for age and sex, with a mean age of roughly 90 years.

The methodological centerpiece of the study was TOMAHAQ, short for triggered by offset, multiplexed, accurate mass, high resolution, and absolute quantification. This targeted mass spectrometry technique, which combines tandem mass tags with trigger-peptide detection and sequential MS3 fragmentation, allows highly specific quantification of low-abundance proteins across many samples in a single run. Using this platform, the team successfully quantified an ATIP peptide sequence, ANLKNPQIMYLEQELESLK, in 12 of the 60 participants, and quantified the type 2 receptor peptide GNSTLATTSK in 58 participants. Amyloid-beta and tau burdens were measured by the Rush Alzheimer’s Disease Center using immunohistochemistry and image analysis across eight brain regions.

The results were striking. ATIP levels showed a significant negative correlation with amyloid-beta load in the midfrontal gyrus, where the peptides were quantified, and with amyloid scores averaged across all eight brain regions. The correlation was strong, with a Spearman coefficient of −0.837 for the midfrontal region and −0.872 for the overall score. Critically, the association endured after statistical adjustment for age and angiotensin receptor blocker use, two potential confounders. When the researchers examined users and non-users of the drugs separately, the inverse correlation persisted in both groups and appeared even more pronounced among the drug users.

Not every question was resolved. The study found no significant correlation between ATIP and type 2 receptor protein levels, and no association between ATIP and tau tangle densities. The authors offer several possible explanations: the type 2 receptor is expressed at very low levels in the adult brain and declines further with age, making accurate quantification difficult; receptor protein abundance may not track receptor activity; and ATIP may exert biological effects independent of the receptor, as suggested by mouse studies in which ATIP’s anti-inflammatory benefits persisted even when the receptor was pharmacologically blocked. Detection of the ATIP peptide itself was limited to 12 of 60 samples, reflecting the technical challenge of measuring scarce proteins in postmortem tissue, although participants with and without detectable ATIP did not differ significantly in amyloid burden.

The researchers caution that the study is exploratory, cross-sectional, and small, and that correlational findings cannot establish causality. Postmortem tissue also captures only a snapshot of dynamic processes occurring during life, and the lack of a cognitively normal control group leaves open whether low ATIP detection is specific to Alzheimer’s disease. Still, the strengths are notable: this is the first direct measurement of ATIP in human Alzheimer’s brain tissue, the design controlled for key demographic factors and drug exposure, and the observed inverse correlation was strong and robust to adjustment. If replicated in larger and more diverse cohorts with longitudinal designs and functional models, ATIP could emerge as a novel target for understanding, and potentially modulating, the amyloid pathology that lies at the heart of Alzheimer’s disease.

Subject of Research: The association between frontal cortex ATIP protein levels and amyloid-beta burden in postmortem brains of older adults with Alzheimer's disease

Article Title: Higher Frontal Cortex Angiotensin Type 2 Receptor‐Interacting Protein (ATIP) Levels Are Associated With a Lower Amyloid‐Beta Burden in Postmortem Brains of Older Adults With Alzheimer's Disease

Article References: Cosarderelioglu, C., Kreimer, S., Plaza‐Rodriguez, A. I., Iglesias, P. A., Talbot, C. C., Jr., Siragy, H. M., Ubaida‐Mohien, C., Grodstein, F., Ferrucci, L., Bennett, D. A., Walston, J., & Abadir, P. (2026). Higher Frontal Cortex Angiotensin Type 2 Receptor‐Interacting Protein ( ATIP ) Levels Are Associated With a Lower Amyloid‐Beta Burden in Postmortem Brains of Older Adults With Alzheimer's Disease. Aging Cell, 25(9), Article e70686. https://doi.org/10.1111/acel.70686

Image Credits: AI Generated

DOI: 10.1111/acel.70686

Keywords: Alzheimer's disease, ATIP, angiotensin II type 2 receptor, amyloid-beta, brain renin-angiotensin system, postmortem brain, TOMAHAQ mass spectrometry, angiotensin receptor blockers, tau pathology, neurodegeneration, aging, MTUS1 gene