PT  - JOURNAL ARTICLE
AU  - Karin Legerstee
AU  - Jason Sueters
AU  - Gert-Jan Kremers
AU  - Jacob P. Hoogenboom
AU  - Adriaan B Houtsmuller
TI  - Correlative light and electron microscopy reveals fork-shaped structures at actin entry sites of focal adhesions
AID  - 10.1101/2022.04.27.489664
DP  - 2022 Jan 01
TA  - bioRxiv
PG  - 2022.04.27.489664
4099  - http://biorxiv.org/content/early/2022/04/28/2022.04.27.489664.short
4100  - http://biorxiv.org/content/early/2022/04/28/2022.04.27.489664.full
AB  - Focal adhesions (FAs) are the main cellular structures to link the intracellular cytoskeleton to the extracellular matrix. FAs mediate cell adhesion, are important for cell migration and are involved in many (patho)-physiological processes. Here we examined FAs and their associated actin fibres using correlative fluorescence and scanning electron microscopy (SEM). We used fluorescence images of cells expressing paxillin-GFP to define the boundaries of FA complexes in SEM images, without using SEM contrast enhancing stains. We observed that SEM contrast was increased around the actin fibre entry site in 98% of FAs, indicating increases in protein density and possibly also phosphorylation levels in this area. In nearly three quarters of the FAs, these nanostructures had a fork shape, with the actin forming the stem and the high contrast FA areas the fork. In conclusion, the combination of fluorescent and electron microscopy allowed accurate localisation of a highly abundant, novel fork structure at the FA-actin interface.Competing Interest StatementThe authors have declared no competing interest.