title: The intracellular tyrosine kinase Brk sensitizes non-transformed cells to inducers of apoptosis.
abstract: The intracellular tyrosine kinase Brk is expressed in regenerating epithelial tissues with highest levels in the gastrointestinal tract and skin. In these tissues, Brk is restricted to epithelial cells that are exiting the cell cycle and undergoing terminal differentiation. While not expressed in mammary gland, Brk expression is often induced in primary breast tumors and breast tumor cell lines. To identify potential oncogenic functions of Brk, we utilized the immortalized Rat1a rat fibroblast cell line that is highly sensitive to transformation. We generated Rat1a cell lines that stably overexpress wild-type and activated Brk, and we analyzed their growth properties and ability to undergo apoptosis in response to stress and DNA damage. Overexpression of Brk did not induce anchorage-independent growth, and no changes in cell morphology or cell cycle progression were observed. However, when constitutively expressed, Brk sensitized Rat1a cells to a variety of apoptotic stimuli including serum deprivation and a combination of UV irradiation and serum starvation. These findings indicate that Brk does not promote proliferation of non-transformed cells, but plays a positive role in the regulation of the apoptotic response to DNA-damage and stress.
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois, USA.
authors.forename: Andrea
authors.initials: A
authors.lastname: Haegebarth
authors.forename: Rafael
authors.initials: R
authors.lastname: Nunez
authors.forename: Angela L
authors.initials: AL
authors.lastname: Tyner
mesh_terms: D000818:Animals; D017209:Apoptosis; D002454:Cell Differentiation; D002460:Cell Line; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D004249:DNA Damage; D005347:Fibroblasts / Q000378:metabolism; D005434:Flow Cytometry; D015151:Immunoblotting; D008856:Microscopy, Fluorescence; D009154:Mutation; D019814:Myristic Acid / Q000737:chemistry; D009363:Neoplasm Proteins / Q000378:metabolism / Q000502:physiology*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D012190:Retroviridae / Q000235:genetics; D013997:Time Factors; D014443:Tyrosine / Q000737:chemistry; D014466:Ultraviolet Rays; D018909:src Homology Domains
chemical_list: D009363:Neoplasm Proteins; D019814:Myristic Acid; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; C088375:PTK6 protein, human