Strategies for media.ng the toxicity of prion proteins. Katrina A. Diaz Burke Group Literature Seminar 11/23/13

Transcription

1 Strategies for media.ng the toxicity of prion proteins Katrina A. Diaz Burke Group Literature Seminar 11/23/13

2 PrP c vs. PrP sc hmp://en.wikipedia.org/wiki/prnp PrP (prion protein or protease- resistant protein); CD230 Physiological role not well understood Exists in mul.ple isoforms, 208 AA long GPI anchor to membrane

3 Proposed func.ons of PrPc T cell ac.va.on and hemopoie.c stem cell differen.a.on Cellular trafficking via clathrin- dependent endocytosis, cell signaling Behavior, sleep, and long term memory Synap.c ac.vity, and neuronal excitability Linden et al. (2008). P hysiol Rev 88: Suppression of apoptosis Westergard L, Christensen HM, Harris DA (2007). Biochim Biophys Acta. 1772: hmp://en.wikipedia.org/, hmp://

4 PrPc vs. PrPsc PrPsc (scrapie) isoform Toxic conforma.onal isoform B- sheet dominated Protease- resistant aggrega.on behavior hmp://intheochem.fc.ul.pt/research/mms.html

5 Proposed mechanisms of toxicity LOF GOF SOF Westergard L, Christensen HM, Harris DA (2007). Biochim Biophys Acta. 1772:

6 Template- directed refolding model Maintained conversion and nucleated polymeriza.on requires ini.al seed- - REVERSIBLE Aguzzi, A., Sigurdson, C., & Heikenwaelder, M. (2008). Annu. Rev. pathmechdis. Mech. Dis., 3,

7 Transmissible spongiform encephalopathies hmp:// Creutzfeldt- Jakob Disease (CJD) Variant Creutzfeldt- Jakob Disease (vcjd) Gerstmann- Straussler- Scheinker Syndrome Fatal Familial Insomnia Kuru Bovine Spongiform Encephalopathy (BSE) Chronic Was.ng Disease (CWD) Scrapie Transmissible mink encephalopathy Feline spongiform encephalopathy Ungulate spongiform encephalopathy

8 Drug- based, cellular assay of the neurodegenera.ve phenotype G418 Massignan, T. et al. J Biol Chem. 2010;285: Zeocin

9 ΔCR- dependent hypersensi.vity cis, WT rescue in trans TUNEL assay: fluorescence assay that detects DNA fragmenta.on indica.ng dying cells Biasini, E. et al (2012). PloS one, 7(3), e33472.

10 Cis toxicity of ΔCR and trans rescuing ac.vity of WT PrP in HEK293 cells Biasini, E. et al (2012). PloS one, 7(3), e33472.

11 Models for ΔCR PrP cis- toxicity and WT PrP trans- rescue Biasini, E. et al (2012). PloS one, 7(3), e33472.

12 POM monoclonal an.bodies Development of an.bodies to probe the role of domains in binding of PrP c to PrP sc and cause toxicity Monoclonal made from clones of immune cells, monovalent affinity Polymenidou, M. et al. PLoS ONE 3, e3872 (2008)

13 Binding of POM an.body ligands can be toxic to neural.ssue Sona., T. et al. (2013). Nature, 501(7465),

14 Cerebellar organotypic cultured slices show toxic effects of POM1 binding Sona., T. et al. (2013). Nature, 501(7465),

15 Immunostaining for neural.ssue marker NeuN shows POM1 toxicity Sona., T. et al. (2013). Nature, 501(7465),

16 POM1 is dose- dependent and can be protected against with exogenous PrP Sona., T. et al. (2013). Nature, 501(7465),

17 Protec.ng against POM1 toxicity using various an.bodies and compounds Sona., T. et al. (2013). Nature, 501(7465),

18 In vivo toxicity of POM1 Sona., T. et al. (2013). Nature, 501(7465),

19 POM1 induces brain lesions in vivo that can be protected against by exogenous PrP Sona., T. et al. (2013). Nature, 501(7465),

20 Conclusions FT region is the effector domain of PrP c - mediated neuronal death An.bodies bind to GD but FT must be present for toxicity to occur GD ligand binding toxicity may mimic binding of PrP c to PrP sc Therapeu.c implica.ons Soluble PrP c may reduce toxicity by binding up free PrP sc, preven.ng interac.on with membrane PrP c An.- GD autoimmunity may cause neurodegenera.on

21 Soluble prion protein inhibits amyloidogenesis of Aβ1 42 Nieznanski, K. et al. (2012). Journal of Biological Chemistry, 287(40),

22 Soluble prion protein inhibits toxicity of Aβ1 42 in cell culture Nieznanski, K. et al. (2012). Journal of Biological Chemistry, 287(40),

23 Outlook Cause for muta.on and misfolding How to prevent misfolding to begin with? Soluble WT prion protein as a therapeu.c in the clinic Issues with foreign protein Protease degrada.on Gene therapy- - overexpression of PrP c could make it worse, quicker infec.on Small molecule mimics of PrP c?