Paula Saa

Summary

Affiliation: American Red Cross
Location: Rockville, USA
Summary:
My research activities over the last 12 years have focused on the study of neurodegenerative diseases and in particular, transmissible spongiform encephalopathies (TSE), which include among others, the bovine spongiform encephalopathy (BSE) in cows and the Creutzfeldt-Jacob disease (CJD) in humans.
I co-invented a new biochemical system to replicate prions in vitro, the Protein Misfolding Cyclic Amplification (PMCA). I successfully applied this new technology to investigate several phenomena associated with prion diseases, including the study of the biological barrier between mammalian species for prion propagation and the molecular basis of prion strain diversity. By means of the PMCA I could multiply prions in vitro in an autocatalytic fashion and demonstrate the self-propagating properties of this agent. Additionally, I showed that the material generated under these conditions shared the same biological and biochemical properties as the naturally generated prions, including the ability to infect wild-type animals. These findings represented the first time that infectious prions were generated in the test tube and provided the most compelling evidence in favor of the prevalent hypothesis in the prion field, the protein-only hypothesis enunciated by Dr. Stanley Prusiner. I also applied the PMCA to detect prions biochemically in the blood of terminally sick animals and to discriminate between healthy and infected individuals during the pre-clinical phase of the disease. This accomplishment not only represented the biochemical detection of prions in a biological fluid for the first time, but also opened the possibility of developing an early non-invasive diagnostic test for animal and human prion diseases. Since its publication, the PMCA has been successfully incorporated by many different laboratories in the field of neurodegeneration to study other aspects of the prion biology.
Recently, I have shown that different mouse prion strains rely to a different extent on accessory molecules (i.e. RNA, DNA and synthetic polynucleotides) for efficient in vitro replication, and that these molecules do not modify the strain-specific properties, but participate in prion conversion as reaction catalysts. These findings significantly contributed to understand the mechanism of prion replication.
As a Scientist II in the laboratory of Dr. Larisa Cervenakova at the American Red Cross, I work in the development of early, minimally-invasive diagnostic methods to determine the presence of the infectious prion protein and disease biomarkers in the blood of affected patients during the presymptomatic phase of the disease. In this regard, I have been recently awarded a research grant by the Alliance BioSecure Research Foundation to identify disease-specific biomarkers in blood exosomes obtained from sick and control animals. Moreover, I am investigating the potential risk of chronic wasting disease (CWD) transmission to human beings, as well as the risk of iatrogenic transmission through blood transfusions.
Grants:
RA V1 120725 Sa

Publications

  1. pmc The N-terminal, polybasic region of PrP(C) dictates the efficiency of prion propagation by binding to PrP(Sc)
    Jessie A Turnbaugh
    Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA
    J Neurosci 32:8817-30. 2012
  2. pmc Prion strain discrimination based on rapid in vivo amplification and analysis by the cell panel assay
    Yervand Eduard Karapetyan
    Department of Infectology, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, United States of America
    PLoS ONE 4:e5730. 2009
  3. pmc Cell-free propagation of prion strains
    Joaquin Castilla
    Department of Neurology, University of Texas Medical Branch, Galveston, TX 77555, USA
    EMBO J 27:2557-66. 2008
  4. pmc Crossing the species barrier by PrP(Sc) replication in vitro generates unique infectious prions
    Joaquin Castilla
    Department of Neurology, University of Texas Medical Branch, Galveston, TX 77555, USA
    Cell 134:757-68. 2008
  5. ncbi request reprint Protein misfolding cyclic amplification for diagnosis and prion propagation studies
    Joaquin Castilla
    Univeristy of Texas, Medical Branch, Galveston, 77555, USA
    Methods Enzymol 412:3-21. 2006
  6. ncbi request reprint Ultra-efficient replication of infectious prions by automated protein misfolding cyclic amplification
    Paula Saa
    George and Cynthia Mitchell Center for Alzheimer Disease and Related Neurodegenerative Disorders, Department of Neurology, University of Texas Medical Branch, Galveston, Texas 77555, USA
    J Biol Chem 281:35245-52. 2006
  7. ncbi request reprint Presymptomatic detection of prions in blood
    Paula Saa
    George and Cynthia Mitchell Center for Alzheimer s disease research, Department of Neurology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555 0646, USA
    Science 313:92-4. 2006
  8. ncbi request reprint Detection of prions in blood
    Joaquin Castilla
    Department of Neurology, University of Texas Medical Branch, 301 University Boulevard, Galveston, Texas, 77555 0646, USA
    Nat Med 11:982-5. 2005
  9. ncbi request reprint Cyclic amplification of protein misfolding and aggregation
    Paula Saa
    Department of Neurology, University of Texas Medical Branch, Galveston, TX, USA
    Methods Mol Biol 299:53-65. 2005
  10. ncbi request reprint In vitro generation of infectious scrapie prions
    Joaquin Castilla
    Department of Neurology, University of Texas Medical Branch, Galveston, Texas 77555, USA
    Cell 121:195-206. 2005

Collaborators

Detail Information

Publications12

  1. pmc The N-terminal, polybasic region of PrP(C) dictates the efficiency of prion propagation by binding to PrP(Sc)
    Jessie A Turnbaugh
    Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA
    J Neurosci 32:8817-30. 2012
    ..It may be possible to specifically target this region for treatment of prion diseases as well as other neurodegenerative disorders due to β-sheet-rich oligomers that bind to PrP(C)...
  2. pmc Prion strain discrimination based on rapid in vivo amplification and analysis by the cell panel assay
    Yervand Eduard Karapetyan
    Department of Infectology, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, United States of America
    PLoS ONE 4:e5730. 2009
    ..We show that in these mice the four prion strains examined are rapidly and faithfully amplified and can subsequently be discriminated by a cell-based procedure, the Cell Panel Assay...
  3. pmc Cell-free propagation of prion strains
    Joaquin Castilla
    Department of Neurology, University of Texas Medical Branch, Galveston, TX 77555, USA
    EMBO J 27:2557-66. 2008
    ..These results provide additional support for the prion hypothesis and indicate that strain characteristics can be faithfully propagated in the absence of living cells, suggesting that strain variation is dependent on PrP(Sc) properties...
  4. pmc Crossing the species barrier by PrP(Sc) replication in vitro generates unique infectious prions
    Joaquin Castilla
    Department of Neurology, University of Texas Medical Branch, Galveston, TX 77555, USA
    Cell 134:757-68. 2008
    ..Our results indicate that PMCA is a valuable tool for the investigation of cross-species transmission and suggest that species barrier and strain generation are determined by the propagation of PrP misfolding...
  5. ncbi request reprint Protein misfolding cyclic amplification for diagnosis and prion propagation studies
    Joaquin Castilla
    Univeristy of Texas, Medical Branch, Galveston, 77555, USA
    Methods Enzymol 412:3-21. 2006
    ..We also describe in detail the technical and methodological aspects of PMCA, as well as its application in automatic and serial modes that have been developed with a view to improving disease diagnosis...
  6. ncbi request reprint Ultra-efficient replication of infectious prions by automated protein misfolding cyclic amplification
    Paula Saa
    George and Cynthia Mitchell Center for Alzheimer Disease and Related Neurodegenerative Disorders, Department of Neurology, University of Texas Medical Branch, Galveston, Texas 77555, USA
    J Biol Chem 281:35245-52. 2006
    ..Therefore, PMCA offers great promise for the development of highly sensitive, specific, and early diagnosis of transmissible spongiform encephalopathy and to further understand the molecular basis of prion propagation...
  7. ncbi request reprint Presymptomatic detection of prions in blood
    Paula Saa
    George and Cynthia Mitchell Center for Alzheimer s disease research, Department of Neurology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555 0646, USA
    Science 313:92-4. 2006
    ..The ability to detect prions biochemically in the blood of infected but not clinically sick animals offers a great promise for the noninvasive early diagnosis of TSEs...
  8. ncbi request reprint Detection of prions in blood
    Joaquin Castilla
    Department of Neurology, University of Texas Medical Branch, 301 University Boulevard, Galveston, Texas, 77555 0646, USA
    Nat Med 11:982-5. 2005
    ..These findings represent the first time that PrP(Sc) has been detected biochemically in blood, offering promise for developing a noninvasive method for early diagnosis of prion diseases...
  9. ncbi request reprint Cyclic amplification of protein misfolding and aggregation
    Paula Saa
    Department of Neurology, University of Texas Medical Branch, Galveston, TX, USA
    Methods Mol Biol 299:53-65. 2005
    ....
  10. ncbi request reprint In vitro generation of infectious scrapie prions
    Joaquin Castilla
    Department of Neurology, University of Texas Medical Branch, Galveston, Texas 77555, USA
    Cell 121:195-206. 2005
    ..These findings demonstrate that prions can be generated in vitro and provide strong evidence in support of the protein-only hypothesis of prion transmission...
  11. pmc Strain-specific role of RNAs in prion replication
    Paula Saa
    The Scripps Research Institute, Scripps Florida, Department of Infectology, Jupiter, Florida, USA
    J Virol 86:10494-504. 2012
    ..We hypothesize that RNA molecules may act as catalysts of prion replication and that variable capacities of distinct prion strains to utilize different cofactors may explain strain-specific dependency upon RNA...