鈴木 江津子

Sulf1 is an extracellular sulfatase that regulates cell signaling by removing 6- O -sulfates from heparan sulfate. Although the roles of Sulf1 in neural development have been studied extensively, its functions in the adult brain remain largely unknown. Here, we report the effects of Sulf1 disruption on the neuronal properties of the medium spiny neurons (MSNs) in the nucleus accumbens (NAc) shell, one of the regions highly expressing Sulf1 . We separately labeled MSNs expressing dopamine D1 receptors (D1-MSNs) or D2 receptors (D2-MSNs) by injecting adult male Drd1-Cre and Drd2-Cre mice with a Cre-dependent AAV vector expressing a red fluorescent protein, mCherry, and examined their electrophysiological properties by means of whole-cell patch-clamp recording. In the D2-MSNs, Sulf1 disruption led to drastic changes in neural firing responses to depolarizing current injections: in the Sulf1 knockout mice, the rheobase was smaller than in the wild-type mice, but the number of action potentials elicited by depolarization did not increase at larger current injections. In the D1-MSNs, Sulf1 disruption resulted in more depolarized resting membrane potentials and increase in the AMPA/NMDA ratio. These results suggest that Sulf1 is essential for regulation of neuronal excitability and glutamatergic transmission of NAc MSNs in adult mice and implicate the potential roles of Sulf1 in NAc circuit activity, reward-aversion behaviors, and psychiatric disorders such as schizophrenia and drug addiction. Significance Statement Heparan sulfate plays critical roles in neural differentiation, axon guidance, synaptogenesis, and neurotransmission. Sulf1 is an extracellular sulfatase that removes 6- O -sulfate from heparan sulfate, thereby regulating various cellular functions. Although its roles during development have been studied extensively, its functions in the adult brain remain largely unknown. Here, we examined the electrophysiological properties of medium spiny neurons in the nucleus accumbens shell of adult mice by means of whole-cell patch-clamp recording. We found that Sulf1 disruption led to changes in neuronal excitability and glutamatergic transmission in medium spiny neurons. This study demonstrates the roles of the Sulf1 gene in neuronal activities at the cellular level, providing an important clue toward understanding the functions of Sulf1 in the adult brain.

<jats:p>Dopamine neurons play crucial roles in pleasure, reward, memory, learning, and fine motor skills and their dysfunction is associated with various neuropsychiatric diseases. Dopamine receptors are the main target of treatment for neurologic and psychiatric disorders. Antipsychotics that antagonize the dopamine D2 receptor (DRD2) are used to alleviate the symptoms of these disorders, but may also sometimes cause disabling side effects such as parkinsonism (catalepsy in rodents). Here we show that GPR143, a G-protein-coupled receptor for L-3,4-dihydroxyphenylalanine (L-DOPA), expressed in striatal cholinergic interneurons enhances the DRD2-mediated side effects of haloperidol, an antipsychotic agent. Haloperidol-induced catalepsy was attenuated in male<jats:italic>Gpr143 gene</jats:italic>-deficient (<jats:italic>Gpr143<jats:sup>−/y</jats:sup></jats:italic>) mice compared with wild-type (Wt) mice. Reducing the endogenous release of L-DOPA and preventing interactions between GPR143 and DRD2 suppressed the haloperidol-induced catalepsy in Wt mice but not<jats:italic>Gpr143<jats:sup>−/y</jats:sup></jats:italic>mice. The phenotypic defect in<jats:italic>Gpr143<jats:sup>−/y</jats:sup></jats:italic>mice was mimicked in cholinergic interneuron-specific<jats:italic>Gpr143<jats:sup>−/y</jats:sup></jats:italic>(<jats:italic>Chat-cre;Gpr143<jats:sup>flox/y</jats:sup></jats:italic>) mice. Administration of haloperidol increased the phosphorylation of ribosomal protein S6 at Ser<jats:sup>240/244</jats:sup>in the dorsolateral striatum of Wt mice but not<jats:italic>Chat-cre;Gpr143<jats:sup>flox/y</jats:sup></jats:italic>mice. In Chinese hamster ovary cells stably expressing DRD2, co-expression of GPR143 increased cell surface expression level of DRD2, and L-DOPA application further enhanced the DRD2 surface expression. Shorter pauses in cholinergic interneuron firing activity were observed after intrastriatal stimulation in striatal slice preparations from<jats:italic>Chat-cre;Gpr143<jats:sup>flox/y</jats:sup></jats:italic>mice compared with those from Wt mice. Together, these findings provide evidence that GPR143 regulates DRD2 function in cholinergic interneurons and may be involved in parkinsonism induced by antipsychotic drugs.</jats:p><jats:p><jats:bold>Significance Statement</jats:bold>Dopamine neuron systems play crucial roles in the control of multiple functions including cognition, fine motor skills and behavioral flexibility, and are involved in neurologic and psychiatric disorders. Antipsychotics are used to alleviate the positive symptoms of schizophrenia and other psychiatric disorders. The therapeutic efficacy of these drugs is related to their antagonistic activities against D2 receptors (DRD2), but disabling side effects may also be caused by DRD2 blockade in multiple dopaminergic pathways. L-DOPA receptor GPR143 when coupled with DRD2 potentiates DRD2-mediated signaling. The neuronal pathways is involved in the GPR143 function, however, have not yet been identified. Here, we identified cholinergic interneurons as the neural circuits in which DRD2 coupled with the L-DOPA receptor GPR143 mediates haloperidol-induced catalepsy.</jats:p>