# ERM proteins support perinuclear actin rim formation

## TL;DR

This study reveals that ERM proteins help form a perinuclear actin rim, linking actin filaments to the nuclear envelope in melanoma and HeLa cells.

## Contribution

The novel finding is that ERM proteins, not Emerin, are involved in perinuclear actin rim formation at the nuclear envelope.

## Key findings

- ERM proteins localize to the nuclear envelope in melanoma cells.
- Knockdown of ERM proteins reduces perinuclear actin rim levels.
- Overexpression of ERM proteins increases rim formation in HeLa cells.

## Abstract

The interaction of actin filaments with the nuclear envelope is essential for diverse cellular processes, including cell migration, nuclear positioning, and transcriptional control. The main studied mechanism that links F-actin to the nucleus is the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex. Recently, the formation of a perinuclear actin rim has been identified in various cell types in response to external force or migration signals. This rim depends on the activation of the actin nucleator Inverted formin 2 (INF2) by calcium influx. However, it is unclear how the rim is coupled to the nuclear envelope. Here, we show that the nuclear membrane protein Emerin, which has an actin-binding domain, is not required for the perinuclear actin rim formation. Interestingly, we found that the Ezrin-Radixin-Moesin (ERM) proteins, known to link actin filaments to the cell membrane, are also localized to the nuclear envelope in melanoma cells. Knockdown of ERM proteins led to a reduction in the rim levels, while overexpression of ERM proteins increased the perinuclear actin rim levels. Overexpression of Ezrin also improved the rim formation in HeLa cells upon addition of a calcium ionophore. Thus, the ERM proteins appear to participate in a mechanism that links actin filaments to the nuclear envelope.