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Inducible and Reversible Dominant-negative (DN) Protein Inhibition
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Tob proteins suppress steroid hormone receptor-mediated transcriptional activation

Hisaya Kawate1, Yin Wu, Keizo Ohnaka

  • 1Department of Geriatric Medicine, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.

Molecular and Cellular Endocrinology
|January 25, 2005
PubMed

Insights

Tob proteins Tob1 and Tob2 inhibit sex steroid hormone action in bone formation by suppressing receptor activity. This suggests Tob family proteins negatively regulate bone metabolism and hormone signaling.

Area of Science:

  • Molecular endocrinology
  • Bone biology
  • Cellular regulation

Background:

  • Sex steroid hormones are crucial for bone metabolism, but their molecular mechanisms are not fully understood.
  • Tob proteins are known regulators of cell proliferation and differentiation, particularly in osteoblasts.

Purpose of the Study:

  • To investigate the functional relationship between steroid hormone receptors and Tob proteins in osteoblasts.
  • To elucidate the role of Tob proteins in mediating sex steroid hormone action on bone formation.

Main Methods:

  • Luciferase assays were used to assess transcriptional activation mediated by steroid hormone receptors.
  • MC3T3-E1 osteoblastic cells were utilized to study protein interactions and cellular responses.
  • Confocal laser scanning microscopy observed the localization and interaction of androgen receptor (AR) with Tob1.

Main Results:

  • Tob1 and Tob2, but not PC3, suppressed steroid hormone receptor-dependent transcriptional activation in osteoblastic cells.
  • Mutated Tob proteins with alterations in the LXXLL motif retained inhibitory activity.
  • Tob1 was observed to inhibit the nuclear foci formation of dihydrotestosterone-bound AR.

Conclusions:

  • Tob family proteins negatively regulate sex steroid hormone action in the context of bone formation.
  • Tob proteins may play a significant role in modulating the effects of hormones on osteoblast function and bone metabolism.

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