The Dual Role of BCL-2 Proteins in Regulating BAX Priming in Human Embryonic Stem Cells (2014)

Undergraduates: Meera Patel, Dr. Vivian Gama

Faculty Advisor: Mohanish Deshmukh
Department: Psychology & Neuroscience

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Human embryonic stem (hES) cells are unique¿they are the precursors of life but are also primed to undergo rapid cell death by apoptosis. Recent findings show that hES cells maintain an important pro-apoptotic protein called BAX at the Golgi apparatus in a constitutively active state that promotes their ability to undergo rapid cell death. The present study explored two groups of proteins in the BCL-2 family known to interact with BAX in other cell types in order to understand whether these proteins function in hES cells to maintain BAX in a constitutively active state and keep active BAX from triggering cell death in the absence of appropriate stimuli. The proteins of inquiry include pro-apoptotic BH3-only proteins BID, BIM, and PUMA and anti-apoptotic BCL-2 family proteins BCL-2, BCL-Xl, and MCL-1. Immunofluorescence and immunoprecipitation techniques were used to visually and qualitatively confirm protein interactions with BAX. The results suggest that pro-apoptotic proteins BIM and PUMA colocalize with active BAX at the Golgi apparatus in hES cells, indicating an interaction with active BAX. They are also localized to some extent at the mitochondria. Furthermore, some of the total cellular BIM and PUMA protein is binding directly to active BAX, indicating a direct interaction. Neither BID nor the anti-apoptotic proteins were found to localize to the Golgi apparatus or bind to active BAX. Overall, these findings help to illuminate more about the basic biology of hES cells.