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- Title
- CHARACTERIZING THE FUNCTION OF THE N-TERMINAL DOMAIN OF OMI/HTRA2.
- Creator
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Nguyen, Christine, Zervos, Antonis, University of Central Florida
- Abstract / Description
-
The yeast two-hybrid system was used to isolate and characterize protein interactors of the N-terminal domain of the serine protease Omi/HtrA2 (high temperature requirement protein A2) encompassing amino acids 31-133. This large domain of Omi/HtrA2 is usually cleaved and removed through autoproteolysis to produce the mature form of the protein. Whether the N-terminal domain has any function after its removal is unknown. Omi/HtrA2 is involved in a variety of diseases including cancers,...
Show moreThe yeast two-hybrid system was used to isolate and characterize protein interactors of the N-terminal domain of the serine protease Omi/HtrA2 (high temperature requirement protein A2) encompassing amino acids 31-133. This large domain of Omi/HtrA2 is usually cleaved and removed through autoproteolysis to produce the mature form of the protein. Whether the N-terminal domain has any function after its removal is unknown. Omi/HtrA2 is involved in a variety of diseases including cancers, neurodegenerative disorders, and metabolic disorders, but thus far, it is assumed that its normal function is the degradation of specific substrates. To characterize any potential function of Omi/HtrA2's unique amino terminus, specific interactors were isolated. One such interactor was the small GTPase Rab2A protein. We discuss the implications of this interaction and its biological significance.
Show less - Date Issued
- 2017
- Identifier
- CFH2000242, ucf:45971
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000242
- Title
- ISOLATION AND CHARACTERIZATION OF A NOVEL SUBSTRATE FOR THE PRO-APOPTOTIC OMI/HTRA2 PROTEASE.
- Creator
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Ward, Nathan, Zervos, Antonis, University of Central Florida
- Abstract / Description
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Omi, also known as HtrA2, is a mammalian pro-apoptotic mitochondrial protein and a member of the HtrA (high temperature requirement A) family of serine proteases. Omi promotes the caspase-dependent apoptotic pathway through cleavage of IAPs (inhibitor of apoptosis proteins); this cleavage inactivates IAPs and facilitates caspase activity. Omi's proteolytic activity is necessary and essential for its pro-apoptotic function. This study is aimed to further understand the role of Omi in the...
Show moreOmi, also known as HtrA2, is a mammalian pro-apoptotic mitochondrial protein and a member of the HtrA (high temperature requirement A) family of serine proteases. Omi promotes the caspase-dependent apoptotic pathway through cleavage of IAPs (inhibitor of apoptosis proteins); this cleavage inactivates IAPs and facilitates caspase activity. Omi's proteolytic activity is necessary and essential for its pro-apoptotic function. This study is aimed to further understand the role of Omi in the cytoplasm by using the yeast two-hybrid system to identify novel Omi interactors/substrates. A HeLa (cervical carcinoma cell line) cDNA library was screened using Omi as a "bait" protein. One of the proteins indentified in this screen as a strong Omi interactor was the S5a protein and was selected for further analysis. S5a is a soluble cytosolic mammalian protein and a component of the proteasome's 19S regulatory subunit. The proteasome is a large cytosolic protein complex responsible for the controlled degradation of damaged or denatured cellular proteins. Further characterization of the interaction through an in vitro proteolytic assay demonstrated that Omi can cleaves recombinant S5a protein. This data suggests that S5a is a bona fide substrate of Omi that is degraded upon induction of apoptosis. It also provides a new mechanism that leads to the inactivation of the proteasome during cell death.
Show less - Date Issued
- 2012
- Identifier
- CFH0004208, ucf:44971
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004208
- Title
- NOVEL PROTEIN-PROTEIN INTERACTIONS REGULATE THE PROTEOLYTIC ACTIVITY OF THE PRO- APOPTOTIC SERINE PROTEASE, OMI/HTRA2.
- Creator
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singh, supriya, Zervos, Antonis, University of Central Florida
- Abstract / Description
-
Omi/HtrA2 is a mitochondrial serine protease with high homology to the bacterial HtrA proteins. Omi promotes caspase-dependent apoptosis by binding and degrading IAPs-inhibitor of apoptosis proteins. Omi can also induce caspase-independent apoptosis but the actual mechanism is still unknown. IAP's are not the only substrates cleaved by Omi. There are at least two more known substrates of Omi, the HAX-1 and the ped/pea-15 proteins. HS1-associated protein X-1 (HAX-1) is a mitochondrial protein,...
Show moreOmi/HtrA2 is a mitochondrial serine protease with high homology to the bacterial HtrA proteins. Omi promotes caspase-dependent apoptosis by binding and degrading IAPs-inhibitor of apoptosis proteins. Omi can also induce caspase-independent apoptosis but the actual mechanism is still unknown. IAP's are not the only substrates cleaved by Omi. There are at least two more known substrates of Omi, the HAX-1 and the ped/pea-15 proteins. HS1-associated protein X-1 (HAX-1) is a mitochondrial protein, degraded by Omi after induction of caspase-dependent apoptosis. Ped/pea-15 is also an anti-apoptotic protein and is cleaved by Omi after induction of caspase-independent apoptosis. The proteolytic activity of Omi is necessary and essential for its pro-apoptotic function. Recent studies suggest the proteolytic activity of Omi is regulated by specific protein-protein interactions. Presenilin was identified to be such a regulator of Omi. It binds to the PDZ domain of Omi via its carboxy-terminus and this interaction significantly increases the proteolytic activity of the enzyme. My project was aimed to investigate the normal function of Omi in cell death and the mechanism of its regulation by isolating and characterizing novel Omi interactors. I screened a human melanocyte cDNA library using the yeast-two-hybrid system and Omi as the "bait" protein. Human Rad21 protein was isolated as a specific novel interactor of Omi. Human Rad21 interacted with the PDZ domain of Omi, the part of the protein known to be involved in protein-protein interactions. Human Rad21 is a nuclear protein that plays a role in DNA double-strand break repair and sister chromatid cohesion during metaphase. Several reports suggest hRad21 has also a role in apoptosis; it is cleaved by caspase-3 and part of the protein becomes cytoplasmic. Human Rad21 was not cleaved by Omi in vitro and therefore it is unlikely to be a substrate. When tested in a proteolytic assay Rad21 was able to increase the proteolytic activity of Omi. My work suggests a new mechanism whereby Omi and hRad21 can co-operate to induce cell death. This mechanism necessitates direct interaction of hRad21 with the PDZ domain of Omi resulting in increased proteolytic activity of the enzyme.
Show less - Date Issued
- 2005
- Identifier
- CFE0000586, ucf:46476
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000586
- Title
- CHARACTERIZATION OF A NOVEL INTERACTOR/SUBSTRATE FOR THE PRO-APOPTOTIC SERINE PROTEASE OMI/HTRA2.
- Creator
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Stratico, Valerie Anne, Zervos, Antonis, University of Central Florida
- Abstract / Description
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Omi/HtrA2 is a highly conserved mammalian serine protease that belongs to the HtrA family of proteins. Omi shares homology with the bacterially expressed heat shock protease HtrA, which functions as a protease at higher temperatures and a chaperone at lower temperatures. Additionally, Omi shares sequence similarity with the mammalian homologs L56/HtrA1 and PRSP/HtrA3. Omi was first isolated as an interacting protein of Mxi2, an alternatively spliced form of the p38 stress-activated kinase,...
Show moreOmi/HtrA2 is a highly conserved mammalian serine protease that belongs to the HtrA family of proteins. Omi shares homology with the bacterially expressed heat shock protease HtrA, which functions as a protease at higher temperatures and a chaperone at lower temperatures. Additionally, Omi shares sequence similarity with the mammalian homologs L56/HtrA1 and PRSP/HtrA3. Omi was first isolated as an interacting protein of Mxi2, an alternatively spliced form of the p38 stress-activated kinase, using a modified yeast two-hybrid system. Omi localizes in the mitochondria and in response to apoptotic stimuli the mature form of this protein translocates to the cytoplasm. In the cytoplasm Omi participates in both the caspase-dependent as well as caspase-independent apoptosis. Additionally, recent studies suggest that Omi may have another unique function, maintaining homeostasis within the mitochondria. In an effort to further elucidate the function of Omi, a yeast two-hybrid screening was performed to isolate novel interacting proteins. This screening identified a novel protein (HOPS), as a specific interactor of Omi. The predicted amino acid sequence of this protein does not provide any information about its potential function in mammalian cells. However, experiments show that HOPS is cleaved in vitro by Omi. Furthermore, in response to apoptotic stimuli, HOPS is also degraded in vivo. This study suggests that HOPS could be a physiological substrate of Omi that is cleaved and removed during apoptosis.
Show less - Date Issued
- 2004
- Identifier
- CFE0000144, ucf:46161
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000144
- Title
- Destination Image and Tourist's Imagination: The Forgotten Component.
- Creator
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Khalilzadeh, Jalayer, Pizam, Abraham, Fyall, Alan, Tasci, Asli, Hancock, Peter, University of Central Florida
- Abstract / Description
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The objectives of this dissertation was to 1) develop a comprehensive scale to measure visitors' imagination, 2) investigate the structural relationship between imagination and tourism destination image (TDI) components of cognitive, affective, and conative, 3) compare and contrast the various qualities of vividness, richness, saliency, control, and spatial between imagination and prospection, and 4) study the impact of different information sources on the evolving process of prospection to...
Show moreThe objectives of this dissertation was to 1) develop a comprehensive scale to measure visitors' imagination, 2) investigate the structural relationship between imagination and tourism destination image (TDI) components of cognitive, affective, and conative, 3) compare and contrast the various qualities of vividness, richness, saliency, control, and spatial between imagination and prospection, and 4) study the impact of different information sources on the evolving process of prospection to imagination. By conducting four different studies and seven data collection phases, the imagination scale was developed, validated, and utilized to test the proposed structural and differential hypotheses. In study 1, the phenomenology approach was employed and through a series of interviews, the internal experience of the imagination process was extracted. In study 2, which is composed of two focus groups, the potential manifest variables to measure imagination/prospection were developed and the structure of the questionnaire was designed. In study 3, through 3 data collection phases, two versions of long and short imagination scale questionnaire were validated and the structural relationships between imagination and destination image was investigated. In the final study, utilizing experimental design, hypotheses related to five qualities of imagination were compared to those of prospection. Finally, by adopting an exploratory approach, the impact of different information sources on imagination was investigated. The results of this dissertation indicated that the imagination scale is a reliable and valid scale to be used in various hospitality and tourism consumption contexts. It shows a high discriminant validity with TDI and structurally moderates the inter-relationships of the TDI components. In addition, findings of this dissertation support the theoretical discussions on the differences between imagination and prospection. Finally, the results revealed significant distinctions among image, video, and textual information sources regarding their impact on the quality of the mental image.
Show less - Date Issued
- 2018
- Identifier
- CFE0007207, ucf:52279
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007207
- Title
- STUDIES ON A NOVEL HUMAN CARDIOSPECIFIC TRANSCRIPTION FACTOR AND ITS INVOLVEMENT IN OMI/HTRA2 MEDIATED CELL DEATH.
- Creator
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Puthucode Balakrishnan, Meenakshi, Zervos, Antonis, University of Central Florida
- Abstract / Description
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Omi/HtrA2 is a mitochondrial serine protease that is known to translocate to the cytoplasm upon induction of apoptosis and to activate caspase-dependent and caspase-independent cell death. The molecular mechanism of Omi/HtrA2ÂÂ's function is not clear but involves degradation of specific substrates. These substrates include cytoplasmic, mitochondrial, as well as nuclear proteins. We have isolated a new Omi/HtrA2 interactor, the THAP5 protein. THAP5 is a fifth member of...
Show moreOmi/HtrA2 is a mitochondrial serine protease that is known to translocate to the cytoplasm upon induction of apoptosis and to activate caspase-dependent and caspase-independent cell death. The molecular mechanism of Omi/HtrA2ÂÂ's function is not clear but involves degradation of specific substrates. These substrates include cytoplasmic, mitochondrial, as well as nuclear proteins. We have isolated a new Omi/HtrA2 interactor, the THAP5 protein. THAP5 is a fifth member of a large family of transcription factors that are involved in cell proliferation, apoptosis, cell cycle control, chromosome segregation, chromatin modification and transcriptional regulation. THAP5 is an approximately 50kDa nuclear protein, with a restricted pattern of expression. Furthermore, there is no mouse or rat homolog for this protein. THAP5 mRNA is highly expressed in the human heart but some expression is also seen in the brain and skeletal muscle. The normal function of THAP5 in the heart or heart disease is unknown. THAP5 protein level is significantly reduced in the myocardial infarction (MI) area in the heart of patients with coronary artery disease (CAD). This part of the heart sustains most of the cellular damage and apoptosis. Our data clearly show that THAP5 is a specific substrate of the proapoptotic Omi/HtrA2 protease and is cleaved and removed during cell death. The molecular mechanism of THAP5ÂÂ's function is unclear. THAP5 can bind to a specific DNA sequence and repress transcription of a reporter gene. Our work suggests that THAP5 is a tissue specific transcriptional repressor that plays an important role in the normal function of the human heart as well as in the development of heart disease.
Show less - Date Issued
- 2010
- Identifier
- CFE0003412, ucf:48409
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003412
