Director: Robert E. Burke, MD
Center Title: Mechanisms of dopamine neuron degeneration
To understand the molecular and cellular mechanisms of neuron degeneration in Parkinson’s disease.
The Udall Center at Columbia University was competitively renewed for 2009-2014, and has now completed Year 03 of the renewal award.
The greatest challenge posed by Parkinson’s disease (PD) is to develop therapies that address the underlying degenerative process. The overriding theme of the Udall Center at Columbia is to address this challenge. Our efforts have two guiding principles. The first is that development of such therapies ultimately depends on a better understanding of mechanisms of disease. The second is that patients cannot wait for a full understanding of this disease to be in hand before efforts are made to translate new knowledge into treatments. Based on these principles, our Center consists of four Projects and five Cores that are integrated according to five current central themes in the pathogenesis of PD. Project 1 (Drs. David Sulzer, PhD, and Ana Maria Cuervo, MD, PhD): “Roles for cytosolic dopamine in PD pathogenesis” extends a line of investigation that suggests that “multiple hits”, consisting of mishandling of 1) α-synuclein (α-syn) degradation, 2) cytosolic calcium, and 3) cytosolic dopamine (DA), underlie PD. Project 2 (Dr. William Dauer, MD): “The FADD/Caspase-8 pathway as a mediator of LRRK2 neurotoxicity” proposes to test whether signaling through FADD/caspase-8 is required for the nigrostriatal-related phenotypes seen in PD mutant LRRK2 transgenic mice. Project 3 (Dr. Lloyd Greene, PhD): “Gene regulation in PD” is based on the rationale that neuron degeneration and death, irrespective of the initiating causes, require transcriptional induction of death-associated genes and that such genes and the pathways that are up- and down-stream of them are potential targets for therapeutic intervention in PD. Project 4 (Dr. Robert E. Burke, MD): “Translational approaches to neuroprotection of axons in PD” is the translational Project of our Udall Center. We are developing gene therapy approaches that utilize Akt/mTor kinase signaling pathways to protect neurons and their axons from degeneration. In addition, in the course of this work we have made the observation that these pathways, remarkably, are also capable of inducing new axon growth in injured dopamine neurons. The goal of this Project is to refine these approaches and to develop promising next-generation alternatives. Core A: Administrative Core (Dr. Burke and Ms. Janice Savage) sets policies and standard operating procedures for Center activities, organizes and conducts regular scientific review, and organizes and implements all the necessary forms of scientific communication to make new discoveries and achievements within the Center known to the scientific community and the public. Core B: Neuroscience Core (Dr. Burke) provides general laboratory services including maintenance and repair of all Core laboratory equipment used by the Principal Investigators. Core C: Brain Bank Core (Drs. Jean Paul Vonsattel and Lorraine Clark). This Core provides the Udall Projects of our Center with brain tissue from clinically and genetically well-characterized PD cases. The brain samples have been fully characterized pathologically and by immunostaining for α-synuclein, β-amyloid and tau. In addition, this Core provides fully characterized brain tissue samples, both fixed and frozen, to the wider Udall and PD research communities. Core D: Core for Training in Translational Research (Dr. Burke). There is a significant need to train young investigators in Neuroscience in the translational potential of their research. This need will be addressed by this training Core. This Core provides young investigators salary support to train in the laboratory of one of the Udall Principal Investigators. Core E: PD Patient Fibroblast Core (Drs. Przedborski and Lorraine Clark) collects and stores skin fibroblasts from patients with sporadic PD and from healthy age-matched controls, destined for future genetic, epigenetic, and stem cell reprogramming investigations.
Progress in Project 1. Roles for cytosolic dopamine in PD pathogenesis (David Sulzer, PhD, and Ana Maria Cuervo, MD, PhD)
Drs. Cuervo and Sulzer have made the observations that the LRRK2 sequence contains 8 consensus motifs for targeting to lysosomes via chaperone-mediated autophagy (CMA) and that wildtype LRRK2 is degraded in lysosomes in mouse brain. They have shown that LRRK2 is unique as compared to other CMA substrates. While association of most CMA substrates to lysosomes decreases in the presence of other substrate proteins, due to competition for the receptor for CMA, binding of LRRK2, both wildtype and more so of mutant LRRK2, markedly increases under these conditions. This high local concentration of LRRK2 at the lysosomal membrane exerts an inhibitory effect on CMA. The consequences of this effect are two-fold: the inability to assemble the CMA translocation complex limits the degradation of LRKK2 and other substrate proteins through this pathway. In addition, because LRRK2 interferes with substrate translocation but not with their binding to LAMP-2A, it results in a marked increase in the amount of cytosolic proteins bound to the lysosomal membrane. This combination of reduced uptake and increased binding is particularly toxic for CMA substrates such as α-syn. In the presence of mutant LKRR2, both wild type and mutant forms of α-syn tend to organize in the form of toxic oligomeric species on the surface of lysosomes. High concentrations of wild type LRRK2 have a similar effect on α-syn oligomerization. These findings provide for the first time evidence of a cooperative toxic effect of two PD related proteins enhanced by their coincidence in lysosomes due to targeting to this compartment by CMA.
Progress in Project 3. Gene regulation in PD (Lloyd Greene, PhD)
Dr. Greene and his co-investigators have made a number of intriguing observations that link the neurobiology of RTP801 and ATF4, two molecules under study in this Project, with that of parkin. His experiments indicate that parkin controls the levels of RTP801 protein by regulating its degradation. When parkin activity is compromised, RTP801 levels rise, putting neurons at risk of death. Parkin knockdown elevates RTP801 levels while parkin over-expression results in decreased RTP801 protein expression. Furthermore, RTP801 levels are elevated in brains of parkin null mice and preliminary findings indicate that RTP801 is elevated in fibroblasts from patients with parkin-associated PD.
Dr. Greene’s studies of RTP801 led to exploration of whether the transcription factor ATF4, which is induced in PD models, may play a role in RTP801 induction. They found that it does not, but new findings identified a potential role for ATF4 in PD. Although ATF4 is often associated with promotion of cell death, they found that knock down of this gene exacerbated death and that its over-expression protected from death in cellular models of PD. Consistent with the up-regulation of ATF4 in his cellular models, Dr. Greene also found elevation of ATF4 protein expression in DA neurons in post-mortem tissue from PD patients (obtained through Core C, Dr. Vonsattel). Exploration of the mechanism by which ATF4 protects from death reveals that it is mediated by increasing the levels of cellular parkin. Ongoing and future studies are exploring means by which ATF4 levels might be elevated in neurons for neuroprotection in PD.
The mutant hR1441G LRRK2 BAC transgenic mice reported in 2009 have been transferred to and are available from the Jackson Laboratory Induced Mutant Resource Repository:
Brain Tissue Resources
During Year 03 of this award, in the Brain Bank Core, 37 brains with Lewy pathology have been collected, genotyped (by Dr. Clark) and banked. From these brains, 1,001 fresh frozen samples were processed and banked. Tissue material is available through the NYBB website: http://www.nybb.hs.columbia.edu/.
Patient Fibroblast and DNA Resources
In the Fibroblast Core, 22 clinically characterized subjects with sporadic PD and 5 controls have had skin biopsies performed and fibroblast lines have been established at the Coriell Institute. This clinical core project collects family and environmental risk information from people with sporadic idiopathic Parkinson’s disease (iPD) for whom there is no known genotype and age/gender matched healthy controls. We use the UK Parkinson’s Disease Society Brain Bank clinical diagnostic criteria for iPD, including excellent response to levodopa. Blood DNA and 3 mm punch skin biopsies are sent overnight to NINDS Human Genetic Research Center at the Coriell Institute (http://ccr.coriell.org/). Additional blood DNA is collected and retained at Columbia University for further studies.
Our Center will continue its work to address five current important themes in the pathogenesis of PD. Each of the Projects builds on discoveries in the genetics of PD. Project 1 (Sulzer & Cuervo) will continue their important work on the degradation of α-synuclein. Projects 2 (Dauer) and 3 (Greene) will explore, in collaboration, mechanisms of LRRK2 toxicity. Project 4 (Burke) will utilize a new hLRRK2(R1441G) BAC transgenic model of PD, in which he has identified a dopaminergic axonopathy, in translational investigations. Project 1 will also examine relationships between processing of synuclein and two important components of the intracellular milieu of dopamine neurons: cytosolic dopamine and calcium. One of the central themes of our Udall Center has been to examine the role of programmed cell death in pathogenesis. This theme has taken on a new importance due to the work of Dr Dauer in Project 3, demonstrating an interaction of LRRK2 with proteins in the extrinsic cell death pathway. Independent lines of investigation in Projects 3 (Greene) and 4 (Burke) have converged on the importance of the survival signaling kinase Akt in the viability of dopamine neurons. The importance of chaperone-mediated autophagy in degradation of synuclein was discovered in Project 1, and the role of macroautophagy in the maintenance of axons has emerged in Project 4. To support the emphasis in the current proposal on the translational implications of our work, the Center now includes a Brain Bank Core (Vonsattel & Clark), a Core for Training in Translational Neuroscience (Burke), and a Fibroblast Core (Przedborski) for the production of human pluripotent cells. Thus the Udall Center at Columbia is poised to discover new approaches to neuroprotection and restoration, and to move these discoveries to the clinic expeditiously.
(Udall Center investigators are indicated in BOLD)
Current therapies for PD treat only its symptoms, not its progression. The goal of our research is to use new knowledge about the mechanisms of neurodegeneration to develop therapies that will block disease progression. We use genetic and neurotoxin models to better understand these mechanisms. We realize that patients cannot wait for us to understand mechanisms completely before we try to develop new therapies. Therefore, we will also go forward with translational research to establish novel pharmacologic and gene therapies.
The second recipient of support through Training Core D as the Columbia Udall Center Postdoctoral Research Scientist, Dr. Sheng-Han Kuo, has successfully applied for and received an AAN Foundation award. He continues his work with Drs. Sulzer and Cuervo in Project 1. In year 04 support will be provided for the third recipient, Adriana Tagliaferro, PhD, to work in Dr. Burke’s Lab. Dr. Tagliaferro will continue her extensive work to characterize the phenotype of the hR1441G LRRK2 BAC transgenic mouse model of PD. The purpose of this Core is to provide cross-training for young MD and PhD scientists in basic and clinical aspects of PD, respectively, in order to enhance their ability to conduct translational research. Dr. Tagliaferro has begun her clinical exposure by taking the 2012 Aspen course Comprehensive Review of Movement Disorders for the Clinical Practitioner, taught by Drs. Stan Fahn, Mark Hallett and Joe Jankovic.
Dr. Sulzer and Dr. James Surmeier, Director of the Udall Center at Northwestern University, successfully applied for an Administrative Supplement to enable them to work together on a collaborative project. The overall goal of the work is to investigate the importance of macroautophagy in PD pathogenesis, a goal that is in keeping with one of the principal research themes of our Center.
Last updated March 20, 2013