Dynamics of GABABR and associated proteins in the postnatal rat cerebellum

Abstract

Before glutamatergic synapses are formed, GABA-mediated signaling is considered to drive cell differentiation in the developing central nervous system (CNS). GABA, a classical inhibitory neurotransmitter, can also depolarize immature cells. Although this shift is mediated by the ionotropic GABA A receptor (GABAAR), recent evidence suggests that the electrical properties of GABAARs can be modulated by the metabotropic GABA B receptor (GABABR). GABABRs are macromolecular complexes, formed by a G protein-coupled receptor and a large number of constituents that interact together and ultimately influence cell identity and behavior. The composition of these complexes exhibits wide spatiotemporal variations; however, the implications of such dynamism during development of the CNS are far from being understood. We have determined total protein expression of some constituents of GABABRs (GABABR1a; GABABR1b, GABABR2; KCTD12) in the developing cerebellum of postnatal rats at 5, 15 and 90 days after birth, by performing Western Blots. Our findings suggest that the expression levels of the core and auxiliary subunits of GABABRs vary ontogenetically. This dynamism was also observed at the mRNA levels by RT-PCR. In addition, multiple immunolabeling followed by confocal microscopy of cerebellar sections showed Purkinje cells as the most dynamic cell type in terms of subcellular localization of the different molecules studied here. Our data support a cell lineage-dependent GABABR regulation.