To ensure reliable synaptic transmission, AMPA receptors are anchored in the postsynaptic density via PSD-95 and transmembrane AMPA receptor regulatory proteins (TARPs). The TARP family comprises six isoforms: four classical (g-2, g-3, g-4, and g-8) and two atypical (g-5 and g-7) TARPs. Their spatial distributions are distinct in the brain, but multiple TARPs are expressed in given neural regions (Fukaya et al., 2005). We have so far studied synaptic expression of individual TARPs, and pursued their roles in AMPA receptor expression by using mutant mice defective in TARP genes. In the cerebellum, TARPg-2 and g-7 are the major isoforms in two major cerebellar neurons, i.e., granule cells and Purkinje cells. They are selectively localized on the postsynaptic membrane of excitatory synapses, and synergistically promote synaptic expression of AMPA receptors. Most notably, GluA2 and GluA3 subunits are severely lost at Purkinje cell synapses in g-2/g-7-double knockout mice, and AMPA receptor-mediated currents at climbing fiber synapses are reduced to 10% of the wild-type levels (Yamazaki et al., 2010). TARPg-7 is also expressed in Bergmann glia, and substantial loss of GluA1 and GluA4 expressions occurs in Bergmann glia of g-7-knockout mice. These observations indicate that TARPs are the major molecular determinants for expression of neuronal and glial AMPA receptors. It should be noted that synaptic expression of AMPA receptors undergoes target cell type-dependent and input source-dependent regulation. This is best known in the hippocampus, where TARPg-8 is the major TARP with additional expression of TARPg-2 and g-3 (Fukaya et al., 2006). To specify the role in the target cell type-dependent regulation, we have recently tested three types of Schaffer collateral synapses in the hippocampal CA1, i.e., perforated and non-perforated synapses on pyramidal cell spines and dendritic synapses on parvalbumin-positive interneurons. In the symposium, we will present our molecular-anatomical data suggesting that TARPg-2 is more potent than TARPg-8 in producing the heterogeneity of AMPA receptor contents among the Schaffer collateral synapses.