Protecting cells from mechanical stress: A novel role of cell-surface receptor LRP1 in extracellular matrix- nuclei communication.

Description

Cellular adaptation to mechanical strain (mechano-adaptation) is increasingly understood to be conferred by Lamin intermediate filament proteins located within the nuclear lamina. Upon mechanical stress, expression levels of Lamin-A and -C changes rapidly to minimise nuclear damage and defects in a cell cycle. However, molecular mechanisms underpinning how cells sense mechanical force and regulate expression levels of Lamin levels remain elusive.

The low-density lipoprotein receptor-related protein 1 (LRP1) is ubiquitously expressed cell-surface receptor that binds to diverse array of extracellular molecules via its large extracellular domain. LRP1 also interacts with various intracellular proteins via its cytoplasmic domain. Deletion of the Lrp1 gene in mice is early embryonically lethal, indicating a critical, but as yet undefined role of LRP1 in biological processes. We recently discovered that LRP1 is a rapid mechano-responder and regulates Lamin-A/C expression in cells. Loss of LRP1 results in deformation and blebbing of the nuclear envelope in fibroblasts and chondrocytes upon mechanical stimulation. Our recent discovery that conditional LRP1 knockout mice have deformation of long bones with marked alteration in Lamin-A/C abundance highlights a LRP1 as a mechano-receptor.

Our hypothesis is that LRP1 senses the extracellular matrix environment, transmits signals inside the cells and protects nucleus from aberrant mechanical force by regulating Lamin-A/C abundance. We will use biochemical, biophysical, proteomics, transcriptomics, imaging analysis and mouse models to understand molecular basis for mechano-transduction via LRP1 and its biological significance. Specific aims are:

1. Identify the LRP1 intracellular interactome. The student will identify cytosolic molecules that bind to intracellular domain of LRP1 using mass-spectrometry (collaborator in Denmark).

2. Determine the role of LRP1 in biophysical properties of cell and nuclear membranes upon local (single cell level) and global (tissue level) mechanical stimulation. Fluorescent imaging analysis and atomic force microscopy will be employed to measure Lamin levels and cell membrane stiffness (expertise provided by secondary supervisor).

3. Elucidate the impact of LRP1 loss on the transcriptomic landscape upon mechanical stimulation. (Expertise provided by tertiary supervisor).

4. Delineate the role of LRP1 on cellular mechano-adaptation in mouse in vivo. The student will histologically examine various tissues from LRP1 knockout mice.

This study will generate insight into fundamental processes of cellular mechano-adaptation, which plays a critical role in formation, maintenance, and regeneration of our body. Our exciting recent discoveries in this rapidly evolving field have led us to establish new collaborations which ensure that we can successfully complete the project and exploit these new developments.