# The RNA-binding protein RNP1A is essential and interacts with contractility kit proteins to facilitate cell mechanics

## TL;DR

This study shows that the RNA-binding protein RNP1A is crucial for cell mechanics and shape changes by interacting with contractility kits in Dictyostelium cells.

## Contribution

The novel contribution is the discovery that RNP1A is essential for cell mechanics and interacts with contractility kit proteins to regulate cell shape and function.

## Key findings

- RNP1A knockdown in Dictyostelium cells leads to reduced proliferation, adhesion, and defective cytokinesis.
- RNP1A interacts with IQGAP1 and contributes to macropinocytosis during cell shape changes.
- Loss of contractility kit proteins results in macropinocytotic defects and altered cell mechanics.

## Abstract

Cell shape regulation is important for many biological processes. Some cell shape-regulating proteins harbor mechanoresponsive properties that enable them to sense and respond to mechanical cues. In Dictyostelium discoideum, mechanoresponsive network proteins formed by proteins such as myosin II, cortexillin I and IQGAP1 assemble in the cytoplasm into macromolecular complexes, which we term contractility kits (CKs). In our previous studies, we identified the RNA-binding protein RNP1A as a genetic interactor with the cytoskeletal machinery of the cell and as a biochemical interactor of cortexillin I, using in vivo fluorescence cross-correlation spectroscopy. In this study, we show that Dictyostelium rnp1A knockdown cells have reduced cell proliferation, reduced adhesion, defective cytokinesis, and a gene expression profile that indicates rnp1A knockdown cells shift away from the vegetative growth state. Some of the transcripts RNP1A binds encode proteins involved in macropinocytosis, a crucial cell shape change process. Loss of other CK proteins leads to macropinocytotic defects characterized by reduced macropinocytotic crown size. RNP1A interacts with IQGAP1, leading to crosstalk during macropinocytosis. Overall, RNP1A binds transcripts and contributes to cell mechanics and cell shape change processes through interactions with CK proteins.

Highlighted Article:
The mechanoresponsive machinery of the cell resides in the cytoplasm in contractility kits (CKs). Using Dictyostelium cells, we show that the CK protein RNP1A contributes to cell mechanics, cell shape changes and the vegetative state cell.