Bryostatin 1 induces ubiquitination and proteasome degradation of Bcl-2 in the human acute lymphoblastic leukemia cell line, Reh.

  • Authors:
    • N R Wall
    • R M Mohammad
    • K B Reddy
    • A M Al-Katib
  • View Affiliations

  • Published online on: February 1, 2000     https://doi.org/10.3892/ijmm.5.2.165
  • Pages: 165-236
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Abstract

The ubiquitin-mediated proteolytic system has been implicated in the turnover of a number of intracellular proteins. In the present study, we investigated the novelty and potential role of bryostatin 1, a macrocyclic lactone isolated from the marine bryozoan, Bugula neritina, in inducing the ubiquitin-mediated proteolysis of the oncoprotein Bcl-2. Immunoprecipitation and immunoblotting analyses revealed that Bcl-2 is ubiquitinated following exposure of the acute lymphoblastic leukemia (ALL) cell line Reh to 1 nM bryostatin 1. Bcl-2 protein rapidly decreases to 50% of that recorded in the control after 24 h of bryostatin 1 treatment. In the subsequent 24 h, Bcl-2 protein again rapidly decreases to 6% of its pre-bryostatin 1 level at which time a plateau is reached and maintained for another 72 h. Furthermore, ubiquitin-Bcl-2 conjugates are detected in untreated as well as bryostatin 1 treated cells, indicating that ubiquitin-dependent proteolysis plays a role in the normal turnover of Bcl-2. However, ubiquitin-Bcl-2 conjugates increase in a time-dependent manner following bryostatin 1 treatment. Lactacystin, which inhibits the proteinase activities of the proteasome, inhibited the bryostatin 1-induced decrease of Bcl-2 protein. The effect of bryostatin 1 on the proteolytic efficiency of the 26S proteasome in Reh cell extracts was also investigated and shown to increase following 1 h of bryostatin 1 treatment. Proteolytic activity reached its highest point by 3 h, and subsequently returned to control levels by 12 h, post-bryostatin 1 treatment. In addition, bryostatin 1 treatment of the Reh cell line decreased expression of bcl-2 mRNA within 3 h. However, bcl-2 mRNA expression returned after 24 h. We speculate that this decrease in mRNA together with increased 26S proteolytic activity accounts for the initial rapid decrease recorded in Bcl-2 protein. These findings indicate that bryostatin 1 treatment of Reh ALL cells decreases Bcl-2 expression through two processes: a) enhanced Bcl-2 protein degradation through the activation of the ubiquitin-proteasome pathway and b) decreased bcl-2 mRNA expression.

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Feb 2000
Volume 5 Issue 2

Print ISSN: 1107-3756
Online ISSN:1791-244X

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Spandidos Publications style
Wall N, Mohammad R, Reddy K and Al-Katib A: Bryostatin 1 induces ubiquitination and proteasome degradation of Bcl-2 in the human acute lymphoblastic leukemia cell line, Reh.. Int J Mol Med 5: 165-236, 2000
APA
Wall, N., Mohammad, R., Reddy, K., & Al-Katib, A. (2000). Bryostatin 1 induces ubiquitination and proteasome degradation of Bcl-2 in the human acute lymphoblastic leukemia cell line, Reh.. International Journal of Molecular Medicine, 5, 165-236. https://doi.org/10.3892/ijmm.5.2.165
MLA
Wall, N., Mohammad, R., Reddy, K., Al-Katib, A."Bryostatin 1 induces ubiquitination and proteasome degradation of Bcl-2 in the human acute lymphoblastic leukemia cell line, Reh.". International Journal of Molecular Medicine 5.2 (2000): 165-236.
Chicago
Wall, N., Mohammad, R., Reddy, K., Al-Katib, A."Bryostatin 1 induces ubiquitination and proteasome degradation of Bcl-2 in the human acute lymphoblastic leukemia cell line, Reh.". International Journal of Molecular Medicine 5, no. 2 (2000): 165-236. https://doi.org/10.3892/ijmm.5.2.165