# Changes in protein glycosylation due to translation of mannosidases encoded by circular RNAs

> **NIH NIH R21** · UNIVERSITY OF KENTUCKY · 2024 · $420,750

## Abstract

Summary
Changes in protein N-glycosylation are a hallmark of Alzheimer’s disease (AD), but the molecular mechanisms
for alterations in protein N-glycosylation are unknown. Mannosidases are key enzymes in protein N-glycosylation
that participate in glycan processing in the Golgi. Only two pre-mRNAs involved in protein N-glycosylation form
abundant circular RNAs (circRNAs): MAN2A1 and MAN1A2. CircMAN2A1 expression correlates with
Alzheimer’s disease, whereas circMAN1A2 remains constant. We found that circMAN2A1 is translated after it
undergoes adenosine to inosine RNA editing, catalyzed by ADAR1-p150 (adenosine deaminase acting on RNA).
During AD progression, the overall RNA editing of circRNA increases, suggesting that circRNA-encoded proteins
will be more and more translated. Due to their generation through backsplicing, circMAN2A1 encoded proteins
lack the endoplasmic signal sequence and are cytosolic. Two of the three circMAN2A1 encoded proteins contain
the catalytic active site and could be active. Transfection studies followed by lectin blots showed that
circMAN2A1-encoded proteins change protein N-glycosylation. We hypothesize that the expression of
circMAN2A1-encoded proteins correlates with AD progression and alters protein N-glycosylation. Similarly, the
increase in circRNA editing will increase circMAN1A2-encoded protein expression. The hypothesis will be tested
in two specific Aims, where in Aim#1, we characterize the expression of circMAN2A1 and circMAN1A2 in brain
during AD development using immunohistochemistry, Western blot and RNAseq on tissue from AD subjects,
test their suitability as biomarkers and determine their intracellular localization. In Aim#2, we will determine the
influence of circMAN2A1 and circMAN1A2-encoded proteins on glycan formation, using in vitro assays and cell
transfections followed by glycan analysis.
The work is highly innovative, using the first antisera against circRNA-encoded proteins and investigates for the
first time the role of an endogenous circRNA-encoded protein. It is significant, as it addresses protein N-
glycosylation as a key pathological feature for AD, for which no molecular mechanisms are known so far.

## Key facts

- **NIH application ID:** 10885423
- **Project number:** 1R21AG087332-01
- **Recipient organization:** UNIVERSITY OF KENTUCKY
- **Principal Investigator:** Stefan Stamm
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $420,750
- **Award type:** 1
- **Project period:** 2024-05-01 → 2026-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10885423

## Citation

> US National Institutes of Health, RePORTER application 10885423, Changes in protein glycosylation due to translation of mannosidases encoded by circular RNAs (1R21AG087332-01). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10885423. Licensed CC0.

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