Leucine-Rich Repeat Kinase 2 (LRRK2) is a large protein encompassing multiple functional domains, including kinase and GTPase enzymatic activity and several protein-protein interaction modules. It is expressed in the central nervous system (CNS) and it is among the most important genetic risk factors for Parkinson’s Disease (PD). Recent evidence suggests a link between PD development and defective insulin signalling, but the reason is still unknown. Interestingly, besides being expressed in the CNS, LRRK2 plays a crucial role also in the periphery. Noteworthy, LRRK2 is found in several insulin-sensitive tissues including muscle and adipose tissue where it has been involved in insulin signalling and/or glucose homeostasis. LRRK2 is also expressed in the endocrine pancreas but here its role is completely unknown. Using molecular and pharmacological approaches, the overall aim of this project was to characterize LRRK2 activity in cells involved in glucose homeostasis with a focus on pancreatic -cells, the only cells within the body able to secrete large amounts of insulin, and muscle cells, critical regulators of body glucose homeostasis. Previous studies performed in the laboratory demonstrated for the first time the expression of the protein in pancreatic -cells and the involvement of its kinase activity in the control of glucose-stimulated insulin secretion. Mechanistically, we here demonstrate that LRRK2 phosphorylates RAB8, a small GTP-binding protein involved in the regulation of vesicular trafficking, in a glucose-dependent manner and favors its recruitment to the primary cilium, an antenna-like structure acting as signalling platform to control hormone secretion. Interestingly, LRRK2 controls the ciliary recruitment of signalling proteins including insulin receptor (IR-A) and glucose transporter type 2 (GLUT2), affecting the -cell ability to secrete insulin. Concurrently, we also focused on muscle tissue, a major regulator of systemic glucose homeostasis. Notably, glucose uptake by muscle requires the secretion of insulin. In muscle cells, we provide evidence that LRRK2 is expressed and necessary for the regulation of glucose transporter type 4 (GLUT4) membrane translocation in myoblasts, the progenitors of mature muscle cells. Similarly to -cells, its kinase activity is required for RAB8-mediated ciliogenesis and ciliary localization of the insulin receptor. Interestingly, inhibition of LRRK2 kinase activity leads to failure of these mechanisms and disruption of myoblasts-myotubes differentiation process. Collectively, these data point to LRRK2 as an interesting player in the context of insulin signalling and release. They also suggest that LRRK2 may indirectly contribute to PD development by modulating insulin signalling and glucose homeostasis.
LEUCINE-RICH REPEAT KINASE 2 (LRRK2) AT THE CROSSROAD OF INSULIN SIGNALLING AND PARKINSON S DISEASE / N. Dule ; tutor: C. Perego ; co-tutor: F. Folli ; coordinatore: GD Norata. Dipartimento di Scienze Farmacologiche e Biomolecolari, 2024 Dec 19. 37. ciclo
LEUCINE-RICH REPEAT KINASE 2 (LRRK2) AT THE CROSSROAD OF INSULIN SIGNALLING AND PARKINSON S DISEASE
N. Dule
2024
Abstract
Leucine-Rich Repeat Kinase 2 (LRRK2) is a large protein encompassing multiple functional domains, including kinase and GTPase enzymatic activity and several protein-protein interaction modules. It is expressed in the central nervous system (CNS) and it is among the most important genetic risk factors for Parkinson’s Disease (PD). Recent evidence suggests a link between PD development and defective insulin signalling, but the reason is still unknown. Interestingly, besides being expressed in the CNS, LRRK2 plays a crucial role also in the periphery. Noteworthy, LRRK2 is found in several insulin-sensitive tissues including muscle and adipose tissue where it has been involved in insulin signalling and/or glucose homeostasis. LRRK2 is also expressed in the endocrine pancreas but here its role is completely unknown. Using molecular and pharmacological approaches, the overall aim of this project was to characterize LRRK2 activity in cells involved in glucose homeostasis with a focus on pancreatic -cells, the only cells within the body able to secrete large amounts of insulin, and muscle cells, critical regulators of body glucose homeostasis. Previous studies performed in the laboratory demonstrated for the first time the expression of the protein in pancreatic -cells and the involvement of its kinase activity in the control of glucose-stimulated insulin secretion. Mechanistically, we here demonstrate that LRRK2 phosphorylates RAB8, a small GTP-binding protein involved in the regulation of vesicular trafficking, in a glucose-dependent manner and favors its recruitment to the primary cilium, an antenna-like structure acting as signalling platform to control hormone secretion. Interestingly, LRRK2 controls the ciliary recruitment of signalling proteins including insulin receptor (IR-A) and glucose transporter type 2 (GLUT2), affecting the -cell ability to secrete insulin. Concurrently, we also focused on muscle tissue, a major regulator of systemic glucose homeostasis. Notably, glucose uptake by muscle requires the secretion of insulin. In muscle cells, we provide evidence that LRRK2 is expressed and necessary for the regulation of glucose transporter type 4 (GLUT4) membrane translocation in myoblasts, the progenitors of mature muscle cells. Similarly to -cells, its kinase activity is required for RAB8-mediated ciliogenesis and ciliary localization of the insulin receptor. Interestingly, inhibition of LRRK2 kinase activity leads to failure of these mechanisms and disruption of myoblasts-myotubes differentiation process. Collectively, these data point to LRRK2 as an interesting player in the context of insulin signalling and release. They also suggest that LRRK2 may indirectly contribute to PD development by modulating insulin signalling and glucose homeostasis.File | Dimensione | Formato | |
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