, tetrameric red fluorescent protein; FL, full-length; GFP, green fluorescent protein; HA, hemagglutinin; HEK293, human embryonic kidney cells; KO, knockout; LC3, microtubule-associated protein 1 light chain 3B; LIR, LC3 interaction region; MEF, mouse embryonic fibroblast; PB1, Phox and Bem1; PBS, phosphate-buffered saline; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SMIR, SOD1 mutant interaction region; SOD, superoxide dismutase; UBA, ubiquitin association; WT, wild-type. AbstractThe p62/sequestosome 1 protein has been identified as a component of pathological protein inclusions in neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). P62 has also been implicated in autophagy, a process of mass degradation of intracellular proteins and organelles. Autophagy is a critical pathway for degrading misfolded and/or damaged proteins, including the copper-zinc superoxide dismutase (SOD1) mutants linked to familial ALS. We previously reported that p62 interacted with ALS mutants of SOD1 and that the ubiquitin-association domain of p62 was dispensable for the interaction. In this study, we identified two distinct regions of p62 that were essential to its binding to mutant SOD1: the N-terminal Phox and Bem1 (PB1) domain (residues 1-104) and a separate internal region (residues 178-224) termed here as SOD1 mutant interaction region (SMIR). The PB1 domain is required for appropriate oligomeric status of p62 and the SMIR is the actual region interacting with mutant SOD1. Within the SMIR, the conserved W184, H190 and positively charged R183, R186, K187, and K189 residues are critical to the p62-mutant SOD1 interaction as substitution of these residues with alanine resulted in significantly abolished binding. In addition, SMIR and the p62 sequence responsible for the interaction with LC3, a protein essential for autophagy activation, are independent of each other. In cells lacking p62, the existence of mutant SOD1 in acidic autolysosomes decreased, suggesting that p62 can function as an adaptor between mutant SOD1 and the autophagy machinery. This study provides a novel molecular mechanism by which mutant SOD1 can be recognized by p62 in an ubiquitin-independent fashion and targeted for the autophagy-lysosome degradation pathway. Keywords: autophagy, familial amyotrophic lateral sclerosis, mutant superoxide dismutase 1, sequestosome 1/p62.

Endogenous neuropeptide Y (NPY) exerts long-lasting spinal inhibitory control of neuropathic pain, but its mechanism of action is complicated by the expression of its receptors at multiple sites in the dorsal horn: NPY Y1 receptors (Y1Rs) on post-synaptic neurons and both Y1Rs and Y2Rs at the central terminals of primary afferents. We found that Y1R-expressing spinal neurons contain multiple markers of excitatory but not inhibitory interneurons in the rat superficial dorsal horn. To test the relevance of this spinal population to the development and/or maintenance of acute and neuropathic pain, we selectively ablated Y1R-expressing interneurons with intrathecal administration of an NPY-conjugated saporin ribosomal neurotoxin that spares the central terminals of primary afferents. NPY-saporin decreased spinal Y1R immunoreactivity but did not change the primary afferent terminal markers isolectin B4 or calcitonin-gene-related peptide immunoreactivity. In the spared nerve injury (SNI) model of neuropathic pain, NPY-saporin decreased mechanical and cold hypersensitivity, but disrupted neither normal mechanical or thermal thresholds, motor coordination, nor locomotor activity. We conclude that Y1R-expressing excitatory dorsal horn interneurons facilitate neuropathic pain hypersensitivity. Furthermore, this neuronal population remains sensitive to intrathecal NPY after nerve injury. This neuroanatomical and behavioral characterization of Y1R-expressing excitatory interneurons provides compelling evidence for the development of spinally-directed Y1R agonists to reduce chronic neuropathic pain.

Sepsis is a leading cause of death, which is characterized by uncontrolled inflammatory response. In this study, we report that caveolin-1, a major component of caveolae, is a critical survival factor of sepsis. We induced sepsis using a well established sepsis animal model, cecal ligation and puncture (CLP). CLP induced 67% fatality in caveolin-1 null mice, but only 27% fatality in wild type littermates (p ‫؍‬ 0.015). Further studies revealed that mice deficient in caveolin-1 exhibited marked increase in tumor necrosis factor-␣ and interleukin-6 production 20 h following CLP treatment, indicating uncontrolled inflammatory responses in the absence of caveolin-1. Caveolin-1 null mice also had a significant increase in bacteria number recovered from liver and spleen, indicating elevated bacterial burdens. In addition, caveolin-1 null mice had a 2-fold increase in thymocyte apoptosis compared with wild type littermates, indicating caveolin-1 as a critical modulator of thymocyte apoptosis during sepsis. In conclusion, our findings demonstrate that caveolin-1 is a critical protective modulator of sepsis in mice. Caveolin-1 exerts its protective function likely through its roles in modulating inflammatory response, alleviating bacterial burdens, and suppressing thymocyte apoptosis.Sepsis is one of the major causes of death, which claims over 215,000 lives and costs $16.7 billion per year in America alone (1-3). The death rate from sepsis is high, exceeding 50%, due to poor understanding of the disease (4). Identifying molecules involved in sepsis, especially endogenous protective modulators, is of great importance, not only in understanding the mechanisms but also in providing new insights for efficient therapies.Caveolae, a subset of lipid rafts, are microdomains of the plasma membrane that are enriched in cholesterol and sphingolipids (5). In addition to its specific lipid compositions, caveolae also contain abundant signaling molecules such as nitricoxide synthase (NOS) 3 and TLR4 and Src family tyrosine kinases, which provide a platform for signal transduction. Caveolin-1, a 24-kDa protein, is a major component of caveolae and has been used as a marker protein of caveolae (6). Disruption of the caveolin-1 gene leads to loss of caveolae (7), indicating an essential role of caveolin-1 in caveolae formation. Given the importance of caveolae in signal transduction, it is not surprising that caveolin-1 has been implicated in a variety of cellular processes such as endocytosis, phagocytosis, and cholesterol trafficking (5-6, 8).Evidence from the caveolin-1 null mouse model has established an inhibitory role of caveolin-1 in cell proliferation and tissue homeostasis. For example, mice deficient in caveolin-1 display hypercellularity in lungs and heart (7, 9 -10). A number of studies also suggest a role of caveolin-1 in apoptosis. However, the role of caveolin-1 in regulating apoptotic cell death is controversial and seems to be cell type-specific and depend on stimuli. For example, knockdown of caveolin-1 by short hairpi...

Peripheral inflammation produces a long-lasting latent sensitization of spinal nociceptive neurons, that is, masked by tonic inhibitory controls. We explored mechanisms of latent sensitization with an established four-step approach: (1) induction of inflammation; (2) allow pain hypersensitivity to resolve; (3) interrogate latent sensitization with a channel blocker, mutant mouse, or receptor antagonist; and (4) disrupt compensatory inhibition with a receptor antagonist so as to reinstate pain hypersensitivity. We found that the neuropeptide Y Y1 receptor antagonist BIBO3304 reinstated pain hypersensitivity, indicative of an unmasking of latent sensitization. BIBO3304-evoked reinstatement was not observed in AC1 knockout mice and was prevented with intrathecal co-administration of a pharmacological blocker to the N-methyl-D-aspartate receptor (NMDAR), adenylyl cyclase type 1 (AC1), protein kinase A (PKA), transient receptor potential cation channel A1 (TRPA1), channel V1 (TRPV1), or exchange protein activated by cAMP (Epac1 or Epac2). A PKA activator evoked both pain reinstatement and touch-evoked pERK expression in dorsal horn; the former was prevented with intrathecal co-administration of a TRPA1 or TRPV1 blocker. An Epac activator also evoked pain reinstatement and pERK expression. We conclude that PKA and Epac are sufficient to maintain long-lasting latent sensitization of dorsal horn neurons that is kept in remission by the NPY-Y1 receptor system. Furthermore, we have identified and characterized 2 novel molecular signaling pathways in the dorsal horn that drive latent sensitization in the setting of chronic inflammatory pain: NMDAR→AC1→PKA→TRPA1/V1 and NMDAR→AC1→Epac1/2. New treatments for chronic inflammatory pain might either increase endogenous NPY analgesia or inhibit AC1, PKA, or Epac.

Neuropeptide Y (NPY) is present in the superficial laminae of the dorsal horn and inhibits spinal nociceptive processing, but the mechanisms underlying its anti-hyperalgesic actions are unclear. We hypothesized that NPY acts at neuropeptide Y1 receptors in dorsal horn to decrease nociception by inhibiting substance P (SP) release, and that these effects are enhanced by inflammation. To evaluate SP release, we used microdialysis and neurokinin 1 receptor (NK1R) internalization in rat. NPY decreased capsaicin-evoked SP-like immunoreactivity in microdialysate of the dorsal horn. NPY also decreased non-noxious stimulus (paw brush)-evoked NK1R internalization (as well as mechanical hyperalgesia and mechanical and cold allodynia) after intraplantar injection of carrageenan. Similarly, in rat spinal cord slices with dorsal root attached, [Leu31, Pro34]-NPY inhibited dorsal root stimulus-evoked NK1R internalization. In rat dorsal root ganglion neurons, Y1 receptors colocalized extensively with calcitonin gene-related peptide (CGRP). In dorsal horn neurons, Y1 receptors were extensively expressed and this may have masked detection of terminal co-localization with CGRP or SP. To determine whether the pain inhibitory actions of Y1 receptors are enhanced by inflammation, we administered [Leu31, Pro34]-NPY after intraplantar injection of complete Freund's adjuvant (CFA) in rat. We found that [Leu31, Pro34]-NPY reduced paw clamp-induced NK1R internalization in CFA rats but not uninjured controls. To determine the contribution of increased Y1 receptor-G protein coupling, we measured [35S]GTPγS binding simulated by [Leu31, Pro34]-NPY in mouse dorsal horn. CFA inflammation increased the affinity of Y1 receptor G-protein coupling. We conclude that Y1 receptors contribute to the anti-hyperalgesic effects of NPY by mediating inhibition of SP release, and that Y1 receptor signaling in the dorsal horn is enhanced during inflammatory nociception.