Methamphetamine-induced activation of trace amine associated receptor (TAAR) 1 regulates astrocyte excitatory amino acid transporter (EAAT)-2 via differential CREB phosphorylation during HIV-associated neurocognitive disorders (HAND)

Objective: Methamphetamine (METH) abuse commonly results in neurocognitive decline, a characteristic shared with HIV-associated neurocognitive disorders. METH abuse exacerbates HAND partly through glutamate dysregulation. Astrocyte excitatory amino acid transporter (EAAT)-2 is responsible for [greater than] 90% of glutamate uptake from the synaptic environment and is significantly decreased with METH and HIV-1. Our previous work demonstrated astrocyte trace amine associated receptor (TAAR) 1 to be involved in EAAT-2 regulation. Astrocyte EAAT-2 is regulated at the transcriptional level by cAMP responsive element binding (CREB) protein and NF-kB, transcription factors activated by cAMP, calcium and IL-1b. Of these, cAMP and calcium are second messengers initiated via activation of TAAR1, that is upregulated by IL-1b. METH-mediated increases in these second messengers and signal transduction pathways have not been shown to directly decrease astrocyte EAAT-2. Hypothesis: We propose CREB activation serves as a master regulator of EAAT-2 transcription, downstream of METH-induced TAAR1 activation. Materials and Methods: To investigate the temporal order of events culminating in CREB activation, genetically encoded calcium indicators, GCaMP6s, were used to visualize METH-induced calcium signaling in primary human astrocytes. RNA interference targeting cAMP-dependent protein kinase A and calcium/calmodulin kinase II confirmed METH-induced regulation of EAAT-2 and resultant glutamate clearance. Furthermore, we investigated METH-mediated CREB phosphorylation at both serine 133 and 142, the co-activator and co-repressor forms, respectively. Conclusions: Overall, this work revealed METH-induced differential CREB phosphorylation is critical for EAAT-2 regulation, and may serve as a mechanistic target for the attenuation of METH-induced excitotoxicity in the context of HAND.