# Golgi retention of KIT in gastrointestinal stromal tumour cells is phospholipase D activity-dependent

## TL;DR

This study reveals how a mutated KIT protein is retained in the Golgi in gastrointestinal stromal tumor cells, depending on phospholipase D activity.

## Contribution

The study identifies PLD2 as a key mediator in the KITmut retention mechanism in GIST cells.

## Key findings

- KITmut activates PLD2 through PKD2, which is essential for its Golgi/TGN retention.
- Inhibiting PLD activity causes KITmut to be degraded in lysosomes, inactivating its signaling.
- PLD activity is required for γ-adaptin association with GGA1, which mediates KITmut retention.

## Abstract

A constitutively active mutant of the receptor protein tyrosine kinase KIT is a major cause of gastrointestinal stromal tumours (GISTs). Recently, we discovered that, during biosynthetic transport, the KIT mutant (KITmut) is retained in the Golgi/trans-Golgi network (TGN), where it activates downstream molecules. This retention is dependent on the phospholipase Cγ2–protein kinase D2–PI4 kinase IIIβ (PLCγ2–PKD2–PI4KIIIβ) pathway, which KITmut activates at the Golgi/TGN. The activated cascade aberrantly recruits GGA1 and the γ-adaptin subunit of AP1, resulting in KITmut retention in the Golgi/TGN. However, the precise mechanisms, including the mediators and effectors of the pathway, remain unclear. In humans, the phosphatidic acid-generating enzymes, phospholipase D1 (PLD1) and PLD2 are known downstream proteins of PKD. In the presence of the PLD inhibitor CAY10594, KITmut is released from the Golgi/TGN and subsequently degraded in lysosomes, leading to signal inactivation. Knockdown experiments indicated that PLD2 plays a role in KITmut retention. KITmut activates PLD2 through PKD2, but not PI4KIIIβ, for Golgi/TGN retention. PLD activity is required for the association of γ-adaptin with GGA1. Therefore, the KIT–PLCγ2–PKD2 pathway separately activates PLD2 and PI4KIIIβ to recruit γ-adaptin and GGA1. Collectively, these results suggest that KITmut retention is dependent on the activation of the PLCγ2–PKD2–PLD2 cascade in GIST cells.

The online version contains supplementary material available at 10.1038/s41598-025-14739-w.