Defining a role for non-canonical mTORC1 activity at focal adhesions
Lead Research Organisation:
University of Bristol
Department Name: Biochemistry
Abstract
Rapamycin is a drug that was originally isolated from bacteria collected on Easter Island, also known as Rapa Nui. It specifically inhibits the mechanistic Target Of Rapamycin Complex 1 (mTORC1), an evolutionarily conserved protein complex that integrates mitogenic and stress signals to control cell growth and metabolism. Since its discovery forty years ago, rapamycin has been used extensively for its immunosuppressive and antitumour properties. More recently however, it has gained attention as a promising anti-ageing drug. Work in laboratory 'animal' models, such as yeast, flies, fish and mice has shown that treatment with rapamycin has similar effects to caloric restriction which is one of the most robust interventions to promote healthspan and lifespan. Rapamycin treatment in humans is however associated with a number of poorly understood side effects, including impaired wound healing. Such side-effects limit the feasibility of using rapamycin to support healthy human ageing.
In this study, we want to explore the role and regulation of a specific pool of mTORC1 that we have identified. Our recent manuscript described, for the first time, that mTORC1 can be activated at the cell edge, in close proximity to proteins associated with focal adhesions (Rabanal-Ruiz et al, 2021). These are specialist structures responsible for anchoring cells to the extracellular environment. The dynamic nature of these structures is important during cell migration, one of the earliest stages of wound healing to close the wound off to the outside environment. Our preliminary and published data indicates that there is tight reciprocal regulation of mTORC1 activity and focal adhesions; namely, disruption of focal adhesions impairs mTORC1 activation while conversely, inhibition of mTORC1 leads to changes in focal adhesion number, size and localisation. Furthermore, our work indicates that this specific pool of mTORC1 is not controlled via classical regulators, and thus we want to identify exactly how it is controlled.
Given the detrimental impact of rapamycin on wound healing, we propose that the pool of mTORC1 in the vicinity of focal adhesions plays an important and specific role in this process. The aim of this grant is to therefore identify the mechanisms controlling mTORC1 at focal adhesions and determine its physiological role in cell migration and wound healing. These data may inform on the future development of therapeutic options to mitigate the side-effects of rapamycin, allowing its widespread use a healthy ageing intervention.
In this study, we want to explore the role and regulation of a specific pool of mTORC1 that we have identified. Our recent manuscript described, for the first time, that mTORC1 can be activated at the cell edge, in close proximity to proteins associated with focal adhesions (Rabanal-Ruiz et al, 2021). These are specialist structures responsible for anchoring cells to the extracellular environment. The dynamic nature of these structures is important during cell migration, one of the earliest stages of wound healing to close the wound off to the outside environment. Our preliminary and published data indicates that there is tight reciprocal regulation of mTORC1 activity and focal adhesions; namely, disruption of focal adhesions impairs mTORC1 activation while conversely, inhibition of mTORC1 leads to changes in focal adhesion number, size and localisation. Furthermore, our work indicates that this specific pool of mTORC1 is not controlled via classical regulators, and thus we want to identify exactly how it is controlled.
Given the detrimental impact of rapamycin on wound healing, we propose that the pool of mTORC1 in the vicinity of focal adhesions plays an important and specific role in this process. The aim of this grant is to therefore identify the mechanisms controlling mTORC1 at focal adhesions and determine its physiological role in cell migration and wound healing. These data may inform on the future development of therapeutic options to mitigate the side-effects of rapamycin, allowing its widespread use a healthy ageing intervention.
Technical Summary
Inhibition of mTORC1 by rapamycin is one of the most robust interventions to improve healthspan in all model organisms tested, from yeast, to flies, fish and mice. The potential use of rapamycin to support healthy ageing in human populations is however hampered by side-effects such as impaired wound healing.
We have recently identified a spatially-distinct pool of mTORC1 that is activated in the vicinity of focal adhesions, independently of the canonical regulators, Rag GTPases and lysosomes. Focal adhesions are large integrin-based adhesive complexes (IAC) that couple the actin cytoskeleton to the extracellular matrix to facilitate cell adhesion and migration. Our published and preliminary data indicate there is tight reciprocal regulation of mTORC1 activity and focal adhesions; disruption of focal adhesions impairs mTORC1 activation while conversely, inhibition of mTORC1 leads to changes in focal adhesion number, size and localisation.
Using in vitro cell models and in vivo, zebrafish models, we will test the hypothesis that the spatially distinct pool of mTORC1 at focal adhesions controls cell migration in wound healing. We posit that it is inhibition of this pool of mTORC1 that underpins the side-effects of rapamycin treatment. We have put together an innovative, discovery-based research proposal to identify the novel regulators of mTORC1 at focal adhesions, to determine exactly how mTORC1 activity impacts focal adhesion dynamics and ultimately to comprehensively investigate the functional role of mTORC1 at focal adhesions in cell migration in the context of wound healing.
By understanding how mTORC1 activity (and thus it's inhibition via rapamycin) controls cell migration in wound healing, we may reveal targets for the development of therapeutics to mitigate one of the major side-effects of rapamycin. Ultimately this could pave the way for more widespread use of rapamycin as a healthy ageing intervention in human populations.
We have recently identified a spatially-distinct pool of mTORC1 that is activated in the vicinity of focal adhesions, independently of the canonical regulators, Rag GTPases and lysosomes. Focal adhesions are large integrin-based adhesive complexes (IAC) that couple the actin cytoskeleton to the extracellular matrix to facilitate cell adhesion and migration. Our published and preliminary data indicate there is tight reciprocal regulation of mTORC1 activity and focal adhesions; disruption of focal adhesions impairs mTORC1 activation while conversely, inhibition of mTORC1 leads to changes in focal adhesion number, size and localisation.
Using in vitro cell models and in vivo, zebrafish models, we will test the hypothesis that the spatially distinct pool of mTORC1 at focal adhesions controls cell migration in wound healing. We posit that it is inhibition of this pool of mTORC1 that underpins the side-effects of rapamycin treatment. We have put together an innovative, discovery-based research proposal to identify the novel regulators of mTORC1 at focal adhesions, to determine exactly how mTORC1 activity impacts focal adhesion dynamics and ultimately to comprehensively investigate the functional role of mTORC1 at focal adhesions in cell migration in the context of wound healing.
By understanding how mTORC1 activity (and thus it's inhibition via rapamycin) controls cell migration in wound healing, we may reveal targets for the development of therapeutics to mitigate one of the major side-effects of rapamycin. Ultimately this could pave the way for more widespread use of rapamycin as a healthy ageing intervention in human populations.
