# Zinc-Induced PKCδ-dependent Phosphorylation of MTF-1 Promotes Pulmonary Vascular Remodeling in Hypoxic Pulmonary Hypertension

## TL;DR

This study shows how zinc activates a protein called MTF-1 through PKCδ, leading to harmful changes in blood vessels in a lung disease called pulmonary hypertension.

## Contribution

The paper identifies a new zinc/PKCδ/MTF-1/PlGF pathway as a potential therapeutic target for hypoxic pulmonary hypertension.

## Key findings

- Zinc increases intracellular zinc levels and activates PKCδ, which phosphorylates MTF-1 at Ser304.
- Phosphorylated MTF-1 promotes PlGF transcription and PASMCs proliferation under hypoxia.
- Blocking the PKCδ/MTF-1/PlGF pathway reduces vascular remodeling in hypoxic PH models.

## Abstract

Pulmonary hypertension (PH) is driven by pulmonary vascular remodeling, in which the zinc-sensing transcription factor metal-responsive transcription factor 1 (MTF-1) may play a pivotal regulatory role. Rodent models of hypoxia-induced PH and cultured pulmonary arterial smooth muscle cells (PASMCs) were used to investigate zinc-mediated MTF-1 activation. Phos-tag SDS-PAGE, site-directed mutagenesis, Cleavage Under Targets and Tagmentation (CUT&Tag), and pharmacological inhibitors were employed to dissect the PKCδ/MTF-1/placental growth factor (PlGF) pathway. CUT&Tag profiling revealed prominent MTF-1 enrichment at promoter regions under hypoxia, with significant occupancy at the Plgf locus and enrichment of angiogenesis-related genes. Hypoxia increased intracellular zinc levels, activated PKCδ, and triggered phosphorylation of MTF-1 at Ser304. This modification was essential for MTF-1 nuclear translocation and PlGF transcription. Mutation of Ser304 or MTF-1 knockdown suppressed PASMCs proliferation and migration under hypoxia and zinc exposure. Gö 6983 abrogated MTF-1 phosphorylation and downstream responses, and selective knockdown of PKCδ reproduced these effects, confirming PKCδ as the predominant isoform mediating MTF-1 activation. In vivo, MTF-1 and PlGF were upregulated in pulmonary vessels of Su/Hx-PH rats, while APTO-253 treatment attenuated pulmonary vascular remodeling and improved cardiopulmonary hemodynamics in hypoxic mice. This study identified PKCδ-dependent phosphorylation of MTF-1 at Ser304 as a critical mechanism linking zinc accumulation to PlGF-driven PASMCs proliferation. Targeting the zinc/PKCδ/MTF-1/PlGF axis represented a novel therapeutic strategy for hypoxic PH.