# In vivo metabolic labeling of photoreceptor proteins

> **NIH NIH R21** · UNIVERSITY OF IOWA · 2022 · $231,750

## Abstract

Project Summary
The retina is often described as a relatively simple part of the central nervous system. Yet, it is
composed of approximately 100 distinct cell types and we know very little about what
differentiates these cell types from one another at the protein level. The problem with obtaining
proteomic data restricted to a particular cell type is that the cell type of interest must be
physically dissociated from its surrounding tissue before proteins can be extracted and
identified. Attempts to do this invariably lead to cross contamination. A possible solution is
offered by in vivo metabolic labeling, or BONCAT. In this approach non-canonical amino acids
with azide functional groups are incorporated into protein. The azide then serves as a tag that
can be labeled for visualization or affinity purification using click chemistry. In mice, it is possible
to restrict the incorporation of the methionine surrogate, azidonorleucine (ANL), to select cell
types. This is done through the Cre-dependent expression of a mutant methionyl-
acyltransferase (MetRS*) that charges tRNA with ANL instead of methionine. Since only protein
synthesized when ANL is present will be labeled, this provides both temporal and spatial
control. The goal in this project is to adapt this technology to studies of photoreceptors as a test
case for future retinal studies. Mice expressing Cre recombinase in either rods or cones will be
crossed with MetRS* mice. We will validate these novel mouse lines, optimize ANL delivery,
and test the specificity and sensitivity of click chemistry-mediated proteomic data collection. We
expect that adapting this technology to the retina will open the door for both cell-type specific
protein profiling and studies of dynamic protein changes in response to disease or various
environmental stimulation.

## Key facts

- **NIH application ID:** 10425524
- **Project number:** 1R21EY033894-01
- **Recipient organization:** UNIVERSITY OF IOWA
- **Principal Investigator:** Sheila A Baker
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $231,750
- **Award type:** 1
- **Project period:** 2022-05-01 → 2024-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10425524

## Citation

> US National Institutes of Health, RePORTER application 10425524, In vivo metabolic labeling of photoreceptor proteins (1R21EY033894-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10425524. Licensed CC0.

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