Down-regulation of cellular proto-oncogenes during inhibition of rat parotid acinar cell proliferation

Seok Woo Lee, Karnam R. Purushotham, Trevor Littlewood, Gerard Evan, Tivadar Zelles, Jofsef Blazsek, Yoichi Nakagawa, Michael G. Humphreys-Beher

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The role of cell surface galactosyltransferase in mediating isoproterenol-induced parotid gland hypertrophy and hyperplasia was examined in rat parotid gland acinar cells. Introduction of the transferase modifier, α-lactalbumin, or galactosyltransferase-associated kinase inhibitor trifluoperazine, into β-agonist-treated rats prevented acinar cell proliferation as determined by [3H]thymidine incorporation after 96 h of treatment. However, [3H]thymidine incorporation into DNA after 24 h of treatment, with injection of a combination of isoproterenol/α-lactalbumin or isoproterenol/trifluoperazine, was similar to injections of isoproterenol alone; suggesting that acinar cells could be stimuated to undergo a single round of DNA synthesis. Northern blot analysis of myc and fos expression followed a similar pattern of down-regulation to control levels after 96 h but not after 24 h. Hybridization with erb B showed little change with proliferation, confirming previous observations on protein levels of the EGF-receptor in acinar cells. Western blot analysis of nuclear protein expression of myc revealed that isoproterenol caused an increase in a 62-kDa protein which was again down-regulated with inhibition of cell proliferation. Analysis of protein levels of Rb110 protein showed no change in protein level in the nucleus with cell proliferation, but did show an associated increase in protein phosphorylation in response to growth stimulation.

Original languageEnglish
Pages (from-to)115-122
Number of pages8
JournalBBA - Molecular Cell Research
Issue number2
Publication statusPublished - Jun 10 1992



  • Calcium ion
  • Calmodulin serine kinase
  • DNA transcription factor
  • Galactosyltransferase
  • Salicary gland

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

Cite this

Lee, S. W., Purushotham, K. R., Littlewood, T., Evan, G., Zelles, T., Blazsek, J., Nakagawa, Y., & Humphreys-Beher, M. G. (1992). Down-regulation of cellular proto-oncogenes during inhibition of rat parotid acinar cell proliferation. BBA - Molecular Cell Research, 1135(2), 115-122.