# Role of A-Kinase Anchoring Proteins in Hepatotoxin- Induced Liver Fibrosis

> **NIH NIH R21** · CEDARS-SINAI MEDICAL CENTER · 2020 · $250,500

## Abstract

PROJECT SUMMARY
Hepatic stellate cell (HSC) activation is a hallmark of liver fibrosis associated with increased collagen production
and extracellular matrix deregulation. Limited antifibrotic therapies are available. Enhanced HSC activation is
observed in hepatotoxin-related liver fibrosis [carbon-tetrachloride (CCL4) or streptozotocin/high fat diet
(STAM™)-induced] as well as in human liver fibrosis. A-kinase anchoring protein 12 (AKAP12) scaffolds protein
kinases A/(PKA/PKC) and cyclin-D1 (CCND1) and controls cell proliferation/migration/invasiveness. AKAP12
phosphorylation by PKCα inhibits its binding to CCND1 in the cytoplasm, allowing CCND1 nuclear translocation
and cell cycle progression. We recently published that HSC activation caused by liver injury (due to alcohol
treatment or bile duct ligation) induces AKAP12 phosphorylation and inhibits its scaffolding activity towards
CCND1 and PKCα. This effect is observed in HSCs but not in other liver cells. We discovered a novel function
of AKAP12 in scaffolding the collagen chaperone, heat shock protein 47 (HSP47) that was inhibited by AKAP12
phosphorylation during HSC activation. Based on the above, we have investigated AKAP12’s phosphorylation
and scaffolding activity during liver fibrogenesis. Our data demonstrate that CCL4 or STAM™ models of liver
fibrosis exhibit extensive AKAP12 phosphorylation mainly in HSCs. This was associated with a drastic drop in
AKAP12’s scaffolding activity towards CCND1 and HSP47. Increased AKAP12 phosphorylation and loss of its
CCND1/HSP47 scaffolding were also evident in fibrotic human liver. Alterations in AKAP12’s interactions with
kinases, PKCα, G-protein coupled receptor kinase 2 (GRK2) and death-associated protein kinase 1 (DAPK1)
were found in activated HSCs and fibrotic liver. We recently published that AKAP12 was anti-fibrogenic in normal
HSCs but acquired pro-fibrogenic properties during HSC activation. We suspected that this was caused by site-
specific phosphorylation of AKAP12. Using Clustered Regularly Interspaced Short Palindromic Repeats
(CRISPR)-directed mutagenesis in HSCs, we now provide evidence that phospho-site editing restores the loss
of scaffolding activity of AKAP12 towards CCND1 and HSP47 in activated HSCs. Moreover, the phospho-
mutations strongly inhibit growth and HSC activation. AKAP12 phospho-mutations did not affect its interaction
with CCND1 in hepatocytes. We therefore hypothesize that site-specific phosphorylation in fibrotic HSCs may
prevent AKAP12 from scaffolding CCND1 or HSP47, thereby facilitating their growth-promoting and collagen
chaperoning/maturation functions, respectively. To test this hypothesis, we propose to identify specific kinases
that phosphorylate AKAP12 in HSCs and examine how this influences its scaffolding-dependent co-localization
with CCND1, HSP47 and the kinases themselves. We will explore the possibility that blocking AKAP12 phospho-
sites may restore its CCND1/HSP47-scaffolding activity and thereby...

## Key facts

- **NIH application ID:** 10022305
- **Project number:** 5R21ES030534-02
- **Recipient organization:** CEDARS-SINAI MEDICAL CENTER
- **Principal Investigator:** Komal Ramani
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $250,500
- **Award type:** 5
- **Project period:** 2019-09-23 → 2022-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10022305

## Citation

> US National Institutes of Health, RePORTER application 10022305, Role of A-Kinase Anchoring Proteins in Hepatotoxin- Induced Liver Fibrosis (5R21ES030534-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10022305. Licensed CC0.

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