Identification of New Yeast Protein Phosphatases Involved in the Regulation of Bax

• Main Author: Silva, Andreia Pinto da Costa dos Santos
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2015
• Subjects: Adenosine; Aging; Alzheimers disease; Apoptosis; Autophagy; Biology; Cellular biology; Cytochrome; Endoplasmic reticulum; Ethanol; Gerontology; Glucose; Homeostasis; Kinases; Medical imaging; Medicine; Mitochondria; Morphology; Neurosciences; NMR; Nuclear magnetic resonance; Permeability; Phosphatase; Phosphorylation; Physiology; Plasmids; Proteins; Regulation; Tumor necrosis factor-TNF; Yeast
• ISBN: 9798480634860

Apoptosis is a genetically controlled cell suicidal program that is highly orchestrated and which contributes to the elimination of unnecessary or damaged cells in multicellular organisms. In this way the organism is capable to maintain the tissue homeostasis. Key regulators of apoptosis include the Bcl-2 family members, which control the permeabilization of mitochondria and the ensuing release of pro-apoptotic factors. Bax is the major pro-apoptotic member of this family. It is mainly cytosolic and remains inactive in proliferating cells, but is translocated to mitochondria and activated in cells undergoing apoptosis, which ultimately leads to permeabilization of the mitochondrial outer membrane. Bax can be regulated through phosphorylation/dephosphorylation by protein kinases and protein phosphatases that integrate different signaling pathways. Currently, the structure of inactive Bax has been determined, but the structures of its active form are still unsolved. The yeast Saccharomyces cerevisiae, has a high degree of conservation of many cellular processes that share fundamental aspects with mammalian. For this reason it has been widely used for the study of the function and regulation of different Bcl-2 family members. In order to identify novel protein phosphatases involved in the dephosphorylation of Bax, we heterologously expressed human Bax in yeast cells lacking non-essential protein phosphatases and determined whether there were differences in the Bax phosphorylation profile. We found several putative protein phosphatase candidates, such as three yeast protein phosphatases (Pph21p/22p and Pct4p), which have as human orthologs PP2A and WIP1 protein phosphatases, respectively. These two human protein phosphatases have been previously described as involved in the dephosphorylation of Bax, which validates the approach developed to identify new candidate protein phosphatases of Bax. The results will be discussed in terms of the consequences of the regulation of Bax by the protein phosphatases identified.