Marlin-1 a novel RNA binding protein associates with GABA(subB) receptors

Couve A, Restituito S, Brandon JM, Charles KJ, Bawagan H, Freeman KB, Pangalos MN, Calver AR and Moss SJ
Source: J Biol Chem
Publication Date: (2004)
Issue: 279(14): 13934-13943
Research Area:
Cells used in publication:
Neuron, hippo/cortical, rat
Species: rat
Tissue Origin: brain
Nucleofectorâ„¢ I/II/2b
In the following experiments primary rat cortical and hippocampal neurons were used for nucleofection: Nucleofection with FLAG-Marlin-1 revealed a granular expression pattern for the protein. Double immunofluorescence showed a more pronounced co-localization with GABABR2 than with GABABR1. Overexpression of both FLAG-Marlin-1 and Myc-GABABR1 provided further evidence for the co-localization. Transfection with a Myc-GABABR1 C-terminal deletion construct revealed the importance of the C-terminus for the interaction. Transfection with an RNAi construct targeted against Marlin-1 significantly decreased the expression level of the protein and resulted in enhanced levels of GABABR2 without affecting R1 levels.
GABA(subB) receptors are heterodimeric G protein-coupled receptors that mediate slow synaptic inhibition in the CNS. While heterodimerization between GABA(subB) receptor GABA(subB)R1 and GABA(subB)R2 subunits is essential for functional expression, how neurons coordinate the assembly of these critical receptors remains to be established. Here we have identified Marlin-1, a novel GABA(subB) receptor binding protein that associates specifically with the GABA(subB)R1 subunit in yeast, tissue culture cells and neurons. Marlin-1 is expressed in the brain and exhibits a granular distribution in cultured hippocampal neurons. Marlin-1 binds different RNA species including the 3 untranslated regions of both the GABA(subB)R1 and GABA(subB)R2 mRNAs in vitro and also associates with RNA in cultured neurons. Inhibition of Marlin-1 expression via sRNAi technology results in enhanced intracellular levels of the GABA(subB)R2 receptor subunit, without affecting the level of GABA(subB)R1. Together our results suggest that Marlin-1 functions to regulate the cellular levels of GABA(subB) R2 subunits, which may have significant effects on the production of functional GABA(subB) receptor heterodimers. Therefore, our observations provide an added level of regulation for the control of GABA(subB) receptor expression and for the efficacy of inhibitory synaptic transmission.