Gβγ Binds Histone Deacetylase 5 (HDAC5) and Inhibits Its Transcriptional Co-repression Activity

Bryan D Spiegelberg,Heidi E Hamm

doi:10.1074/jbc.m504066200

Abstract

In a yeast two-hybrid screen designed to identify novel effectors of the G betagamma subunit of heterotrimeric G proteins, we found that G betagamma binds to histone deacetylase 5 (HDAC5), an enzyme involved in a pathway not previously recognized to be directly impacted by G proteins. Formation of the G beta1gamma2-HDAC5 complex in mammalian cells can be blocked by overexpression of G alpha(o), and this inhibition is relieved by activation of alpha2A-adrenergic receptor, suggesting that the interaction occurs in a signal-dependent manner. The C-terminal domain of HDAC5 binds directly to G betagamma through multiple motifs, and overexpression of this domain mimics the C terminus of G protein-coupled receptor kinase 2, a known G betagamma scavenger, in its ability to inhibit the G betagamma/HDAC5 interaction. The C terminus of HDAC4 shares significant similarity with that of HDAC5, and accordingly, HDAC4 is also able to form complexes with G beta1gamma2 in cultured cells, suggesting that the C-terminal domain of class II HDACs is a general G betagamma binding motif. Activation of a G(i/o)-coupled receptor results in a time-dependent activation of MEF2C, an HDAC5-regulated transcription factor, whereas inhibition of the interaction with a G betagamma scavenger inhibits MEF2C activity, suggesting a reduced potency of HDAC5-mediated inhibition. Taken together, these data imply that HDAC5 and possibly other class II HDACs can be added to the growing list of G betagamma effectors.

Highlights

In a recent effort to expand our understanding of G␤␥ function, we conducted a yeast two-hybrid screen seeking to identify novel G␤␥
Both G␤␥ and receptor tyrosine kinases modulate the activity of the ␤ isoform of phosphoinositide 3-kinase, and GPCR activation can result in transactivation of receptor tyrosine kinases in the modulation of mitogen-activated protein kinase (MAPK) cascades
Two clones whose expression resulted in reporter gene transcription were found to encode the C-terminal ϳ160 amino acids of histone deacetylase 5 (HDAC5)

Summary

Introduction

In a recent effort to expand our understanding of G␤␥ function, we conducted a yeast two-hybrid screen seeking to identify novel G␤␥-. The interaction was found to be independent of the co-expression of mammalian G␥ (data not shown), suggesting that G␤1 formed a functional dimer with a yeast G␥-like protein in situ and that binding was mediated by G␤ rather than G␥. HA-G␤1 was purified when HDAC5-FLAG was immunoprecipitated, indicating that the proteins can exist in an identical complex in mammalian cells.

Results

Conclusion