RACK1 downregulates levels of the pro-apoptotic protein Fem1b in apoptosis-resistant colon cancer cells

M. Cecilia Subauste, T. Ventura-Holman, L. Du, Jose S. Subauste, Shing Leng Chan, Victor C. Yu, Joseph F. Maher

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Evasion of apoptosis plays an important role in colon cancer progression. Following loss of the Apc tumor suppressor gene in mice, the gene encoding Fem1b is upregulated early in neoplastic intestinal epithelium. Fem1b is a pro-apoptotic protein that interacts with Fas, TNFR1 and apaf-1, and increased expression of Fem1b induces apoptosis of cancer cells. Fem1b is a homolog of FeM-1, a protein in Caenorhabditis elegans that is negatively regulated by ubiquitination and proteasomal degradation. To study Fem1b regulation in colon cancer progression, we used apoptotis-sensitive SW480 cells, derived from a primary colon cancer, and their isogenic, apoptosis-resistant counterparts sW620 cells, derived from a subsequent metastatic lesion in the same patient. Treatment with proteasome inhibitor increased Fem1b protein levels in SW620 cells, but not in SW480 cells. In SW620 cells we found that endogenous Fem1b co-immunoprecipitates in complexes with RACK1, a protein known to mediate ubiquitination and proteasomal degradation of other pro-apoptotic proteins and to be upregulated in colon cancer. Full-length Fem1b, or the N-terminal region of Fem1b, associated with RACK1 when co-expressed in HEK293T cells, and RACK1 stimulated ubiquitination of Fem1b. RACK1 overexpression in SW620 cells led to downregulation of Fem1b protein levels. Conversely, downregulation of RACK1 led to upregulation of Fem1b protein levels, associated with induction of apoptosis, and this apoptosis was inhibited by blocking Fem1b protein upregulation. In conclusion, RACK1 downregulates levels of the pro-apoptotic protein Fem1b in metastatic, apoptosis-resistant colon cancer cells, which may promote apoptosis-resistance during progression of colon cancer.

Original languageEnglish (US)
Pages (from-to)2297-2305
Number of pages9
JournalCancer Biology and Therapy
Volume8
Issue number23
StatePublished - Dec 1 2009
Externally publishedYes

Fingerprint

Apoptosis Regulatory Proteins
Colonic Neoplasms
Down-Regulation
Apoptosis
Ubiquitination
Proteins
Up-Regulation
Caenorhabditis elegans Proteins
Receptors, Tumor Necrosis Factor, Type I
Proteasome Inhibitors
Intestinal Mucosa
Tumor Suppressor Genes

Keywords

  • Colon cancer
  • Fem1b
  • Proteasome
  • RACK1
  • SW480
  • SW620
  • Ubiquitin

ASJC Scopus subject areas

  • Cancer Research
  • Oncology
  • Molecular Medicine
  • Pharmacology

Cite this

Subauste, M. C., Ventura-Holman, T., Du, L., Subauste, J. S., Chan, S. L., Yu, V. C., & Maher, J. F. (2009). RACK1 downregulates levels of the pro-apoptotic protein Fem1b in apoptosis-resistant colon cancer cells. Cancer Biology and Therapy, 8(23), 2297-2305.

RACK1 downregulates levels of the pro-apoptotic protein Fem1b in apoptosis-resistant colon cancer cells. / Subauste, M. Cecilia; Ventura-Holman, T.; Du, L.; Subauste, Jose S.; Chan, Shing Leng; Yu, Victor C.; Maher, Joseph F.

In: Cancer Biology and Therapy, Vol. 8, No. 23, 01.12.2009, p. 2297-2305.

Research output: Contribution to journalArticle

Subauste, MC, Ventura-Holman, T, Du, L, Subauste, JS, Chan, SL, Yu, VC & Maher, JF 2009, 'RACK1 downregulates levels of the pro-apoptotic protein Fem1b in apoptosis-resistant colon cancer cells', Cancer Biology and Therapy, vol. 8, no. 23, pp. 2297-2305.
Subauste MC, Ventura-Holman T, Du L, Subauste JS, Chan SL, Yu VC et al. RACK1 downregulates levels of the pro-apoptotic protein Fem1b in apoptosis-resistant colon cancer cells. Cancer Biology and Therapy. 2009 Dec 1;8(23):2297-2305.
Subauste, M. Cecilia ; Ventura-Holman, T. ; Du, L. ; Subauste, Jose S. ; Chan, Shing Leng ; Yu, Victor C. ; Maher, Joseph F. / RACK1 downregulates levels of the pro-apoptotic protein Fem1b in apoptosis-resistant colon cancer cells. In: Cancer Biology and Therapy. 2009 ; Vol. 8, No. 23. pp. 2297-2305.
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