Biomedical subjects

S Cosulich

Publications and source records attributed to S Cosulich.

3 recordsLinked to original sources

PubMed1999

Bcl-2 regulates a caspase-3/caspase-2 apoptotic cascade in cytosolic extracts.

Apoptosis is accompanied by the activation of a number of apoptotic proteases (caspases) which selectively cleave specific cellular substrates. Caspases themselves are zymogens which are activated by proteolysis. It is widely believed that 'initiator' caspases are recruited to and activated within apoptotic signalling complexes, and then cleave and activate downstream 'effector' caspases. While activation of the effector caspase, caspase-3, has indeed been observed as distal to activation of several different initiator caspases, evidence for a further downstream proteolytic cascade is limited. In particular, there is little evidence that cellular levels of caspase-3 that are activated via one pathway are sufficient to cleave and activate other initiator caspases. To address this issue, the ability of caspase-3, activated upon addition to cytosolic extracts of cytochrome c, to cause cleavage of caspase-2 was investigated. It was demonstrated that cleavage of caspase-2 follows, and is dependent upon, activation of caspase-3. Moreover, the activation of both caspases was inhibited by Bcl-2. Together, these data indicate that Bcl-2 can protect cells from apoptosis by acting at a point downstream from release of mitochondrial cytochrome c, thereby preventing a caspase-3 dependent proteolytic cascade.

Apoptosis↗

PubMed1996

Apoptosis: does stress kill?

A wide variety of cellular stresses can initiate apoptosis, or programmed cell death. Recent work shows that the mechanism involves stress-activated protein kinase pathways, although the targets of these pathways are unknown at present.

Apoptosis↗

PubMed1995

Mutant p53 is not fully dominant over endogenous wild type p53 in a colorectal adenoma cell line as demonstrated by induction of MDM2 protein and retention of a p53 dependent G1 arrest after gamma irradiation.

To determine whether a single mutational event in one p53 gene is sufficient to confer a significant growth advantage on a colonic epithelial cell, the 143(Ala) p53 mutation was previously expressed in the human colonic adenoma derived cell line AA/C1 (which is wild type for p53) and shown to have no effect on it's in vitro or in vivo growth characteristics. In this investigation, by expressing the 175(His), 248(Trp) or 273(His) mutations in the same AA/C1 cell line, we have shown that this failure to affect the growth of the cells was not mutant specific. We have also demonstrated, using induction of MDM2 protein and the ability of the cells to undergo a p53 dependent G1 arrest, that the 143(Ala), 175(His) or 248(Trp) transfected cells retain functional endogenous wild type p53 activity, and suggest that these p53 mutations would not have a fully dominant negative mode of action in vivo. In contrast, one of the two AA/C1 cell lines transfected with the 273(His) mutation did fail to cell cycle arrest after gamma irradiation, indicating that this mutation can act as a dominant negative. However even loss of wild type p53 function in this cell line was insufficient to directly effect the growth rate of the AA/C1 cells, suggesting that acquisition of the 273(His) mutation may contribute to malignant progression through genomic instability (by inhibiting the G1 arrest) and that other mutations are required before outgrowth of the cell population containing the p53 mutation.

Adenoma↗