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Keywords:

  • cerebellum;
  • immunohistochemistry;
  • mGluR1;
  • PLCβ3;
  • Purkinje cell

Abstract

Phospholipase Cβ3 (PLCβ3) and PLCβ4 are the two major isoforms in cerebellar Purkinje cells (PCs), displaying reciprocal expression across the cerebellum. Here, we examined subcellular distribution of PLCβ3 in the mouse cerebellum by producing specific antibody. PLCβ3 was detected as a particulate pattern of immunostaining in various PC elements. Like PLCβ4, PLCβ3 was richly distributed in somatodendritic compartments, where it was colocalized with molecules constituting the metabotropic glutamate receptor (mGluR1) signalling pathway, i.e. mGluR1α, Gαq/Gα11 subunits of Gq protein, inositol 1,4,5-trisphosphate receptor IP3R1, Homer1, protein kinase C PKCγ, and diacylglycerol lipase DAGLα. Unlike PLCβ4, PLCβ3 was also distributed at low to moderate levels in PC axons, which were intense for IP3R1 and PKCγ, low for Gαq/Gα11, and negative for mGluR1α, Homer1, and DAGLα. By immunoelectron microscopy, PLCβ3 was preferentially localized around the smooth endoplasmic reticulum in spines, dendrites, and axons of PCs, and also accumulated at the perisynapse of parallel fibre-PC synapses. Consistent with the ultrastructural localization, PLCβ3 was biochemically enriched in the microsomal and postsynaptic density fractions. These results suggest that PLCβ3 plays a major role in mediating mGluR1-dependent synaptic transmission, plasticity, and integration in PLCβ3-dominant PCs, through eliciting Ca2+ release, protein phosphorylation, and endocannabinoid production at local somatodendritic compartments. Because PLCβ3 can be activated by Gβγ subunits liberated from Gi/o and Gs proteins as well, axonal PLCβ3 seems to modulate the conduction of action potentials through mediating local Ca2+ release and protein phosphorylation upon activation of a variety of G protein-coupled receptors other than mGluR1.