SUMMARY Thiamine monophosphatase (TMPase, also known as Fluoride-Resistant Acid Phosphatase) is a classic histochemical marker of small-diameter dorsal root ganglia neurons. The molecular identity of TMPase is currently unknown. We found that TMPase is identical to the transmembrane isoform of Prostatic Acid Phosphatase (PAP), an enzyme with unknown molecular and physiological functions. We then found that PAP knockout mice have normal acute pain sensitivity but enhanced sensitivity in chronic inflammatory and neuropathic pain models. In gain-of-function studies, intraspinal injection of PAP protein has potent anti-nociceptive, anti-hyperalgesic and anti-allodynic effects that last longer than the opioid analgesic morphine. PAP suppresses pain by functioning as an ecto-5’-nucleotidase. Specifically, PAP dephosphorylates extracellular adenosine monophosphate (AMP) to adenosine and activates A1-adenosine receptors in dorsal spinal cord. Our studies reveal molecular and physiological functions for PAP in purine nucleotide metabolism and nociception and suggest a novel use for PAP in the treatment of chronic pain.

Parkinson's disease, an age-related neurodegenerative disorder, is characterized by the loss of dopamine neurons in the substantia nigra, the accumulation of α-synuclein in Lewy bodies and neurites, and neuroinflammation. While the exact etiology of sporadic Parkinson's disease remains elusive, a growing body of evidence suggests that misfolded α-synuclein promotes inflammation and oxidative stress resulting in neurodegeneration. α-Synuclein has been directly linked to microglial activation in vitro and increased numbers of activated microglia have been reported in an α-synuclein overexpressing mouse model prior to neuronal loss. However, the mechanism by which α-synuclein incites microglial activation has not been fully described. Microglial activation is governed in part, by pattern recognition receptors that detect foreign material and additionally recognize changes in homeostatic cellular conditions. Upon proinflammatory pathway initiation, activated microglia contribute to oxidative stress through release of cytokines, nitric oxide, and other reactive oxygen species, which may adversely impact adjacent neurons. Here we show that microglia are directly activated by α-synuclein in a classical activation pathway that includes alterations in the expression of toll-like receptors. These data suggest that α-synuclein can act as a danger-associated molecular pattern.

Topotecan is a topoisomerase 1 (TOP1) inhibitor that is used to treat various forms of cancer. We recently found that topotecan reduces the expression of multiple long genes, including many neuronal genes linked to synapses and autism. However, whether topotecan alters synaptic protein levels and synapse function is currently unknown. Here we report that in primary cortical neurons, topotecan depleted synaptic proteins that are encoded by extremely long genes, including Neurexin-1, Neuroligin-1, Cntnap2, and GABA A β3. Topotecan also suppressed spontaneous network activity without affecting resting membrane potential, action potential threshold, or neuron health. Topotecan strongly suppressed inhibitory neurotransmission via pre-and postsynaptic mechanisms and reduced excitatory neurotransmission. The effects on synaptic protein levels and inhibitory neurotransmission were fully reversible upon drug washout. Collectively, our findings suggest that TOP1 controls the levels of multiple synaptic proteins and is required for normal excitatory and inhibitory synaptic transmission.synapse | topoisomerase | transcription T opoisomerase inhibitors such as topotecan (Hycamtin) are widely used to treat multiple forms of cancer, including brain metastases, ovarian cancer, and small cell lung cancer (1). Topoisomerases resolve DNA supercoiling during cell division and during gene transcription (2). Type I topoisomerases, encoded by Top1, Top3a, and Top3b in mammals, resolve supercoiling by cleaving a single strand of DNA, whereas type II topoisomerases, encoded by Top2a and Top2b, cleave both DNA strands (2). Recently, both types of topoisomerases were associated with neurodevelopment (3-5). For instance, topoisomerase 1 (TOP1) and topoisomerase 2 (TOP2) inhibitors transcriptionally up-regulate the paternal copy of Ubiquitin-protein ligase E3A (Ube3a) (5), a gene that affects synaptic activity and that is deleted or duplicated in distinct neurodevelopmental disorders (Angelman syndrome and autism, respectively) (6, 7). Moreover, a de novo mutation in Top1 and de novo mutations in genes that interact with Top1 and Top3b were identified recently in patients with autism (8, 9), whereas deletion of Top3b increases the risk for schizophrenia and intellectual disability (10, 11). Top2b is also required for axon outgrowth in different regions of the nervous system and for the survival of postmitotic neurons (12-15).TOP1 is localized primarily in the nucleus of postmitotic neurons and is expressed throughout the developing and adult brain (16), suggesting a nuclear function. Indeed, we recently found that topotecan, a selective TOP1 inhibitor, reduced the expression of extremely long genes (>200 kb) in postmitotic neurons by impairing transcription elongation (17). Topotecan and related camptothecin analogs inhibit TOP1 by covalently trapping the enzyme on DNA (2). TOP1 inhibitors also reduce the expression of long genes in cancer cell lines (17-19), revealing a gene length-dependent component to transcription that is common to sev...

No abstract

No abstract