The unique N-terminal sequence of metallothionein-3 is required to regulate the choice between apoptotic or necrotic cell death of human proximal tubule cells exposed to Cd+2.
This laboratory has shown that MT-3 expression determines the choice between apoptotic or necrotic cell death in Cd(+2)-exposed human proximal tubule cells. Human proximal tubule cells that express MT-3 undergo necrosis when exposed to Cd(+2), while cells that have no basal expression of MT-3 undergo apoptotic cell death. It was also shown that cells which express MT-3 were more sensitive to Cd(+2)-induced cell death than those having no basal expression. In the present study, site directed mutagenesis was used to determine if the unique N-terminal sequence of MT-3 was required for these activities regarding toxicity and cell death. The results demonstrated that HK-2 cells stably transfected with MT-3 that had been modified by converting the 2 prolines at amino acid positions 7 and 9 to threonines was no longer active in promoting necrotic cell death at lower levels of Cd(+2) exposure. This was shown in comparison to cells containing the wild type MT-3 sequence and blank vector controls as regards the % of DAPI-stained fragmented nuclei, DNA laddering, LDH release, caspase-9, and caspase-3 activation. This study demonstrates that the unique N-terminal sequence of MT-3 is required to elicit an effect on the mechanism of Cd(+2)-induced death of the proximal tubule cell. This is the identical sequence that has been shown to be responsible for the growth inhibitory activity of MT-3 in the neural system.
Somji
Seema
S
Department of Pathology, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota 58202, USA.
Garrett
Scott H
SH
Sens
Mary Ann
MA
Sens
Donald A
DA
D000544:Alzheimer Disease / Q000378:metabolism; D017209:Apoptosis; D002104:Cadmium / Q000633:toxicity*; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000473:pathology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D000090023:Metallothionein 3; D016297:Mutagenesis, Site-Directed; D009336:Necrosis; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism
D000090023:Metallothionein 3; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D002104:Cadmium; D007770:L-Lactate Dehydrogenase