| PTPRO, located on the cell membrane, is a typical receptor-type protein tyrosine phosphatases, involved in glomerular albumin permeability and axon growth and guidance. In many tumor cells, the expression of PTPRO is silenced by methylation of CpG islands in promoters and deletion in chromosome. These data have demonstrated the growth-suppressor characteristics of PTPRO that are unique as a classical tumor suppressor. At present, many studies have demonstrated that PTPROt expression increases the susceptibility of cells to apoptosis, inhibites growth and anchorage independence of cells, and negatively regulates cell cycle. However, it is unclear how PTPRO controls cell cycle as a transmembrane protein. c-Abl, a complex protein with multi-domains and functions, belongs to the non-receptor tyrosine kinase family, and it can shuttle between nucleus and cytoplasma depending on its nuclear localization signals and nuclear export signals. It is known that c-Abl targets to the nucleus in the apoptotic response to DNA damage. c-Abl may also be a growth suppressor, which can inhibit cell cycle at the G1 phase.In this thesis, we intended to identify the pathway from cell membrane to nucleus that enables PTPRO to function as a cell cycle regulator. c-Abl may alter its subcellular distribution under specific conditions, and it plays a similar role to PTPRO during cell cycle suppression. To examine whether c-Abl plays a part in the PTPRO-regulated cell cycle progression, we used HeLa cells to carry on the experiments and found that both PTPRO and c-Abl were able to arrest cell cycle, and to downregulate the cell cycle-associated transcription factor E2F1.The results from CoIP assays showed that PTPRO was co-immunoprecipitated with c-Abl. Analysis from immunofluorescence and subcellular extraction demonstrated that PTPRO promoted the targeting of c-Abl to nucleus. Data presented in this thesis suggest that c-Abl may function as a bridge in the process when PTPRO regulates cell cycle. |
PDF Full Text Request