Actin-binding Protein α-Actinin-1 Interacts with the Metabotropic Glutamate Receptor Type 5b and Modulates the Cell Surface Expression and Function of the Receptor

Abstract

Receptors for neurotransmitters require scaffolding proteins for membrane microdomain targeting and for regulating receptor function. Using a yeast two-hybrid screen, alpha-actinin-1, a major F-actin cross-linking protein, was identified as a binding partner for the C-terminal domain of metabotropic glutamate receptor type 5b (mGlu(5b) receptor). Co-expression, co-immunoprecipitation, and pull-down experiments showed a close and specific interaction between mGlu(5b) receptor and alpha-actinin-1 in both transfected HEK-293 cells and rat striatum. The interaction of alpha-actinin-1 with mGlu(5b) receptor modulated the cell surface expression of the receptor. This was dependent on the binding of alpha-actinin-1 to the actin cytoskeleton. In addition, the alpha-actinin-1/mGlu(5b) receptor interaction regulated receptor-mediated activation of the mitogen-activated protein kinase pathway. Together, these findings indicate that there is an alpha-actinin-1-dependent mGlu(5b) receptor association with the actin cytoskeleton modulating receptor cell surface expression and functioning.

Deletion of Densin-180 Results in Abnormal Behaviors Associated with Mental Illness and Reduces mGluR5 and DISC1 in the Postsynaptic Density Fraction

“…Only the amount of α-actinin was significantly reduced in knockout PSD fractions (32%); it was also reduced in total brain homogenates (33%), suggesting that expression or stability of α-actinin is impaired in the absence of densin ( Figure 6 ). α-Actinin has been reported to bind two proteins previously implicated in schizophrenia, DISC1 and mGluR5 (Millar et al, 2003; Cabello et al, 2007). We measured their amounts and found that both DISC1 and mGluR5 are normal in brain homogenates of densin knockout mice, but significantly reduced (~30%) in PSD fractions compared to wild-type ( Figure 6 ).…”

α-Actinin structure and regulation

“…At adhesion sites, including focal adhesions, adherent junctions and hemidesmosomes, the first binding partners of a-actinin to be discovered were cytoplasmic tails of the beta-subunit of integrin and the intracellular adhesion molecule-1 (ICAM-1) [49,51,141]. Many more interactions with transmembrane proteins, most of them adhesion proteins, have been identified since then [16, 50 -52, 54 -62, 142, 143], such as receptors of NMDA [55], adenosine A2A [58], glutamate [62], vinculin [144 -146] and inducible nitric oxide synthase in macrophages [147]. The interactions are typically formed between the negatively charged rod domain and positively charged cytoplasmic peptides, and serve multiple functions, from linking transmembrane proteins to actin cytoskeleton, acting as a scaffold for recruitment of signaling molecules, clustering the adhesion molecules at specific sites, and regulation of the receptor activity.…”

Diversity of Metabotropic Glutamate Receptor–Interacting Proteins and Pathophysiological Functions

“…Thus, a-actinin-4 interacts with group I mGlu receptors (Cabello et al 2007;Francesconi et al 2009a); vimentin with mGlu1b (Francesconi et al 2009b); a/btubulin with mGlu1a/b and mGlu7 (Francesconi et al 2009b); band 4.1 proteins with mGlu1a and mGlu8 (Lu et al 2004;Rose et al 2008); filamin-A with mGlu5 (Enz 2002a), mGlu4, mGlu7, and mGlu8; and microtubule-associated protein 1B (MAP1B) with all group III mGlu subunits (Moritz et al 2009). …”