# REGULATION AND FUNCTION OF RETINAL PHOSPHOINOSITIDES

> **NIH NIH R01** · BAYLOR COLLEGE OF MEDICINE · 2020 · $400,000

## Abstract

The goal is to understand regulation of phosphoinositide synthesis, degradation and localization in the retina
and retinal pigmented epithelium (RPE), and to understand the role of phosphoinositides in retinal signaling,
development, health and disease. By illuminating molecular details of such processes as membrane trafficking,
autophagy, phagocytosis, endocytosis and exocytosis, this understanding can help us better understand how
these processes are disrupted in retinal disease and how therapeutic interventions could make use of them to
preserve vision. The specific aims are: 1. Determine the relationship between each step in the
phototransduction cascade and regulation of PI(3)P PI(4)P, and PI(4,5)P2 regulation in rods. Light,
independently of time-of-day, drives massive increases in the levels of inner segment phosphoinositides.
Preliminary results suggest the signal driving this increase is downstream of the phototransduction cascade,
and our published results demonstrate a critical role for the Class III PI-3-kinase, Vps34. It remains unclear
how light leads to upregulation of the activity of Vps34 or what drives PI(4,5)P2 increases. The following
hypotheses will be tested: A. Transducin activation by photoexcited rhodopsin is essential for the light-driven
increases. B. PDE6 activity is essential for light-driven increases. C. The cyclic nucleotide-gated channel is
essential for the increases. 2. Determine the role of PI(4)P-5 kinase activity in PIP2 (phosphatidylinositol-
(4,5)bisphosphate) regulation in the outer retina and the functional role there of PI(4,5)P2. We will
generate mice with inducible rod-cell- or RPE-cell-specific knockouts of the principal enzyme responsible for
synthesizing PI(4,5)P2 in neurons, PIP-5-kinaseγ, and determine the phenotype with respect to
phosphoinositide levels, cell morphology and survival, protein trafficking, endocytosis, phagocytosis and
autophagy. These experiments will test the following hypotheses: A. PI(4,5)P2 is primarily synthesized in rods
and RPE by the action of the PIP-5-kinaseγ isoform using ATP and PI(4)P as substrates; B. PI(4,5)P2
synthesis is essential for a range of membrane trafficking functions and cell viability. If needed, we will also test
the global knockouts of the α and β isoforms, which are viable, as well as double and triple. 3. Determine the
distinct phosphoinositide-regulated mechanisms of LC3 recruitment and lysosome fusion in
autophagy and phagocytosis. We have found deficiencies in the standard models of LC3 recruitment to
autophagosomes and phagosomes, so we will combine in vivo experiments with experiments with RPE cell
lines to determine which proteins are critical for LC3 recruitment in RPE cells and what sequence of events
leads to this key event in both pathways. We will also identify the PI(3)P binding proteins that are essential for
LC3 recruitment to phagosomes and those that are essential for lysosome fusion of both autophagosomes and
phagosomes.

## Key facts

- **NIH application ID:** 10072476
- **Project number:** 1R01EY031949-01
- **Recipient organization:** BAYLOR COLLEGE OF MEDICINE
- **Principal Investigator:** THEODORE G WENSEL
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $400,000
- **Award type:** 1
- **Project period:** 2020-09-30 → 2024-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10072476

## Citation

> US National Institutes of Health, RePORTER application 10072476, REGULATION AND FUNCTION OF RETINAL PHOSPHOINOSITIDES (1R01EY031949-01). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10072476. Licensed CC0.

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