# Plasma Membrane Targeting and Retargeting of Polarity Proteins

> **NIH NIH R01** · UNIVERSITY OF PITTSBURGH AT PITTSBURGH · 2022 · $320,646

## Abstract

SUMMARY
 Targeting polarity proteins to mutually exclusive plasma membrane (PM) domains is an essential
process for establishing and maintaining cell polarity – a process that is regulated by an ever-expanding
interaction network among polarity proteins and their regulators/effectors. In contrast, much less is known
about how physical interactions between polarity proteins and the PM contribute to this polarization process.
Recent research from the PI’s lab showed that multiple core polarity proteins (“polybasic polarity proteins”)
such as Lgl, aPKC, and Dlg are also inherently membrane-binding proteins. They contain so-called polybasic
domains that specifically and electrostatically target to the PM by binding to PM phospholipids such as PI4P
and PIP2. We have characterized multiple mechanisms that control the polarized electrostatic PM targeting
function of polybasic polarity proteins. We have also discovered an unexpected consequence of such widely
existing electrostatic PM targeting in cell polarity: PM localization of polybasic polarity proteins is highly
susceptible to energetic stresses triggered by hypoxia and ATP inhibition, which induce dynamic turnover of
PM PI4P and PIP2. In this proposal, our goal is to further establish electrostatic PM-targeting as a fundamental
mechanism regulating cell polarity under both normal and energetic stressed conditions. Specifically, we will
investigate:
 1) Diverse mechanisms regulating electrostatic PM targeting in cell polarity. We will focus on the
regulation of electrostatic PM targeting of basolateral polarity protein Dlg which is controlled by
phosphorylation, allosteric regulation of its polybasic domain, and interactions with other basolateral polarity
proteins. We will elucidate how allosteric regulation of electrostatic PM targeting acts as a core mechanism by
which basolateral polarity proteins control each other’s localization and functions.
 2) Control of aPKC phosphorylation by electrostatic PM targeting. aPKC is the key kinase driving cell
polarization and its pseudo-substrate region (PSr) is also a polybasic domain that is allosterically controlled by
Par-6 for both PM targeting and kinase activity. Using a novel inducible polarization system, we will investigate
the hypothesis that Par-6-dependent electrostatic PM targeting of aPKC controls the substrate-specific
phosphorylation of aPKC/Par-6, providing a mechanism of spatiotemporal control of aPKC kinase activity in
cell polarization.
3) Regulation of electrostatic PM retargeting of polybasic polarity proteins. Despite total loss of the PM
targeting function of Lgl and aPKC under hypoxia due to depletion of PM PI4P and PIP2, we found that both
proteins always directly retargeted their original basolateral or apical PM domains once reoxygenation started.
We will investigate both lipid- and protein-based mechanisms that restore and control such polarized PM
retargeting of polybasic polarity proteins. These mechanisms will be critical to...

## Key facts

- **NIH application ID:** 10520488
- **Project number:** 2R01GM121534-05A1
- **Recipient organization:** UNIVERSITY OF PITTSBURGH AT PITTSBURGH
- **Principal Investigator:** Yang Hong
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $320,646
- **Award type:** 2
- **Project period:** 2017-04-01 → 2026-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10520488

## Citation

> US National Institutes of Health, RePORTER application 10520488, Plasma Membrane Targeting and Retargeting of Polarity Proteins (2R01GM121534-05A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10520488. Licensed CC0.

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