Molecular control of cell death

We are interested in the molecular and cellular events involved in the initiation, execution and regulation of cell death in mammalian cells. Our research program focuses on two main facets of this problem: a more fundamental aspect, where we investigate the intracellular signals triggered by amino acids, and a more applied focus, where the impact of the modulation of cell death on the behaviour of hybridoma cells is investigated.

1. Understanding the molecular events responsible for the induction of cell death upon deprivation of the amino acid L-glutamine.

It has been known for the past 50 years that L-glutamine is required for mammalian cell survival. Not only is this amino acid essential for the growth of most cultured cell lines, but decreased blood glutamine levels (resulting from catabolic stress following severe trauma or malnourishment) has also been shown to sensitize cells to undergo programmed cell death, contributing to several diseases such as sepsis, intestinal atrophy and immunodeficiency. Furthermore, glutamine supplementation has been shown to improve the state of the immune system and to prevent some of the side effect associated with chemo/radiotherapy. Surprisingly, the molecular basis of glutamine-mediated cell survival is still poorly understood.

We have recently introduced the mouse hybridoma cell line Sp2/0-Ag14 as a unique model for the study of the molecular events triggered following L-glutamine withdrawal. Our recent work demonstrates that that glutamine deprivation triggers a rapid (<2 hours) apoptotic death program in these cells. Characterization of this phenomenon revealed that glutamine withdrawal triggers an intrinsic apoptotic death pathway. A major focus of our current work is to characterize the cellular "glutamine sensors" which link intracellular glutamine levels to cell survival.

2. Optimization of biotechnologically-relevant mammalian cell lines. Mammalian cell culture is widely used to produce large amounts of proteins of biotechnological or biomedical interest (e.g. monoclonal antibodies). However, cell death by apoptosis has been shown to severely limit the productivity of these cells, both in batch or perfusion cultures. While the induction of apoptotic cell death in long-term culture can be attributed to several factors, the exhaustion of amino acids, notably L-glutamine, from the culture media consitutes an important trigger. New means to improve the viability of cultured cell lines are therefore being sought, either by modifying culture conditions or genetically altering the cells themselves.

One aspect of our research program in centred on investigating the role which apoptosis plays in limiting the viability of cell lines in culture. In particular, we are exploring the molecular pathways responsible for apoptosis in long-term cultured cells. Our goal is to use this newly acquired knowledge to improve cell viability using genetic engineering techniques (e.g. ectopic gene expression). We are also exploring the molecular basis of apoptosis induction in hybridoma cells. Finally, one aspect of our research is to determine the impact that the gene expression profile specific to each hybridoma cell ligne can have on cell behaviour and productivity.

Selected recent publications.

Note: A Star (*) indicates a graduate student. A double star (**) indicates an undergraduate student.

Matthew Mallory*, Kevin Chartrand and Eric R. Gauthier. (2007) GADD153 expression does not necessarily correlate with changes in culture behavior of hybridoma cells.
BMC Biotechnology .7: 89. [PDF]

O.M. Fattah, S.M. Cloutier, C. Kündig, L.M. Felber, C.M. Gygi, P. Jichlinski, H.-J. Leisinger, E.R. Gauthier, J.P. Mach and D. Deperthes. (2006). Peptabody-EGF: a novel apoptosis inducer targeting ErbB1 receptor overexpressing cancer cells. Int. J. Cancer. DOI: 10.1002/ijc.21541.

*P.J. Guérin, T. Furtak**, Kellton Eng** and E.R. Gauthier. (2006). Oxidative stress is not required for the induction of apoptosis upon glutamine starvation of Sp2/0-Ag14 cells Eur. J. Cell. Biol. 85: 355-365.

*Paquette, J. C., P.J. Guérin*, and E.R. Gauthier. (2005). Rapid induction of the intrinsic apoptotic pathway by L-glutamine starvation. J. Cell. Physiol. 202 (3): 912-921.

*Guérin, P.J. and E.R. Gauthier. (2003). Induction of cellular necrosis by the glutathione peroxidase mimetic ebselen. J. Cell. Biochem. 89: 203-211.

*Charbonneau, J.R., T. Furtak**, J. Lefebvre** and E.R. Gauthier. (2003). Bcl-xL expression interferes with the effects of L-glutamine supplementation on hybridoma cultures. Biotechnol. Bioeng. 81: 279-290.

*Charbonneau, J. and E.R. Gauthier. (2001). Protection of hybridoma cells against apoptosis by a loop domain-deficient Bcl-xL protein. Cytotechnology. 37: 41-47. 

*Charbonneau, J. and E.R. Gauthier. (2000). Prolongation of hybridoma cell viability in stationary batch culture by Bcl-xL expression. Cytotechnology. 34(1-2): 131-39.