title: Glutamate receptor activation evokes calpain-mediated degradation of Sp3 and Sp4, the prominent Sp-family transcription factors in neurons.
abstract: Sp-family transcription factors (Sp1, Sp3 and Sp4) contain a zinc-finger domain that binds to DNA sequences rich in G-C/T. As assayed by RT-PCR analysis of mRNA, western-blot analysis, immunofluorescence, and antibody-dependent "supershift" of DNA-binding assays, the prominent Sp-family factors in cerebral neurons were identified as Sp3 and Sp4. By contrast, glial cells were found to express Sp1 and Sp3. We previously showed that the pattern of G-C/T binding activity of Sp-family factors is rapidly and specifically altered by the calcium influx accompanying activation of glutamate receptors. Here, we demonstrate that Sp-factor activity is also lost after a cerebral ischemia/reperfusion injury in vivo. Consistent with its calcium-dependent nature, we found that glutamate's effect on Sp-family factors could be blocked by inhibitors of calpains, neutral cysteine proteases activated by calcium. Purified calpain I cleaved Sp3 and Sp4 into products that retained G-C/T-binding activity, consistent with species observed in glutamate-treated neurons. These data provide details of an impact of glutamate-receptor activation on molecular events connected to gene expression.
authors.affiliation: Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
authors.forename: Xianrong
authors.initials: X
authors.lastname: Mao
authors.forename: Shao-Hua
authors.initials: SH
authors.lastname: Yang
authors.forename: James W
authors.initials: JW
authors.lastname: Simpkins
authors.forename: Steven W
authors.initials: SW
authors.lastname: Barger
mesh_terms: D000818:Animals; D002154:Calpain / Q000502:physiology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000378:metabolism / Q000473:pathology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D018698:Glutamic Acid / Q000494:pharmacology; D002546:Ischemic Attack, Transient / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017470:Receptors, Glutamate / Q000502:physiology*; D015427:Reperfusion Injury / Q000378:metabolism / Q000473:pathology; D016329:Sp1 Transcription Factor / Q000378:metabolism; D051705:Sp3 Transcription Factor / Q000378:metabolism*; D051706:Sp4 Transcription Factor / Q000378:metabolism*
chemical_list: D018690:Excitatory Amino Acid Agonists; D017470:Receptors, Glutamate; D016329:Sp1 Transcription Factor; C497123:Sp3 protein, rat; D051706:Sp4 Transcription Factor; C081928:Sp4 protein, rat; D051705:Sp3 Transcription Factor; D018698:Glutamic Acid; D002154:Calpain