Activating Transcription Factor-6α Deletion Modulates the Endoplasmic Reticulum Stress Response after Spinal Cord Injury but Does Not Affect Locomotor Recovery.

The endoplasmic reticulum stress response (ERSR) is activated in a variety of neurodegenerative diseases and/or traumatic injuries. Subsequent restoration of ER homeostasis may contribute to improvement in the functional outcome of these diseases. We recently demonstrated improvements in hindlimb locomotion after thoracic spinal cord injury (SCI) and implicated oligodendrocyte survival as a potential mechanism using genetic and pharmacological inhibition of the protein kinase ribonucleic acid-like ER kinase- CCAAT/enhancer binding homologous protein (PERK-CHOP) arm of the ERSR. Here, we investigated the contribution of activating transcription factor-6 (ATF6), an ERSR signaling effector comprising the second arm of ERSR, in the pathogenesis of SCI. In contrast to what was seen after attenuation of PERK-CHOP signaling, genetic ablation of ATF6 results in modulation of ERSR and decreased survival in oligodendrocyte precursor cells against ER stress. Further, ATF6 loss delays the ERSR after SCI, potentiates PERK-ATF4-CHOP signaling and fails to improve locomotor deficits. These data suggest that deleting ATF6 levels is unlikely to be a viable therapeutic target to improve functional recovery after SCI.

Inhibition of GADD34, the stress-inducible regulatory subunit of the endoplasmic reticulum stress response, does not enhance functional recovery after spinal cord injury.

Activation of the endoplasmic reticulum stress response (ERSR) is a hallmark of various pathological diseases and/or traumatic injuries. Restoration of ER homeostasis can contribute to improvement in the functional outcome of these diseases. Using genetic and pharmacological inhibition of the PERK-CHOP arm of the ERSR, we recently demonstrated improvements in hindlimb locomotion after spinal cord injury (SCI) and implicated oligodendrocyte survival as a potential mechanism. Here, we investigated the contribution of stress-inducible PPP1R15A/GADD34, an ERSR signaling effector downstream of CHOP that dephosphorylates eIF2α, in the pathogenesis of SCI. We show that although genetic ablation of GADD34 protects oligodendrocyte precursor cells (OPCs) against ER stress-mediated cell death in vitro and results in differential ERSR attenuation in vivo after SCI, there is no improvement in hindlimb locomotor function. Guanabenz, a FDA approved antihypertensive drug, was recently shown to reduce the burden of misfolded proteins in the ER by directly targeting GADD34. Guanabenz protected OPCs from ER stress-mediated cell death in vitro and attenuated the ERSR in vivo after SCI. However, guanabenz administration failed to rescue the locomotor deficits after SCI. These data suggest that deletion of GADD34 alone is not sufficient to improve functional recovery after SCI.

Kinetic isotope effects support the twisted amide mechanism of Pin1 peptidyl-prolyl isomerase.

The Pin1 peptidyl-prolyl isomerase catalyzes isomerization of pSer/pThr-Pro motifs in regulating the cell cycle. Peptide substrates, Ac-Phe-Phe-phosphoSer-Pro-Arg-p-nitroaniline, were synthesized in unlabeled form, and with deuterium-labeled Ser-d3 and Pro-d7 amino acids. Kinetic data were collected as a function of Pin1 concentration to measure kinetic isotope effects (KIEs) on catalytic efficiency (kcat/Km). The normal secondary (2°) KIE value measured for the Ser-d3 substrate (kH/kD = 1.6 ± 0.2) indicates that the serine carbonyl does not rehybridize from sp(2) to sp(3) in the rate-determining step, ruling out a nucleophilic addition mechanism. The normal 2° KIE can be explained by hyperconjugation between Ser α-C-H/D and C═O and release of steric strain upon rotation of the amide bond from cis to syn-exo. The inverse 2° KIE value (kH/kD = 0.86 ± 0.08) measured for the Pro-d7 substrate indicates rehybridization of the prolyl nitrogen from sp(2) to sp(3) during the rate-limiting step of isomerization. No solvent kinetic isotope was measured by NMR exchange spectroscopy (kH2O/kD2O = 0.92 ± 0.12), indicating little or no involvement of exchangeable protons in the mechanism. These results support the formation of a simple twisted amide transition state as the mechanism for peptidyl prolyl isomerization catalyzed by Pin1. A model of the reaction mechanism is presented using crystal structures of Pin1 with ground state analogues and an inhibitor that resembles a twisted amide transition state.

Post-hospital medical respite care and hospital readmission of homeless persons.

Medical respite programs offer medical, nursing, and other care as well as accommodation for homeless persons discharged from acute hospital stays. They represent a community-based adaptation of urban health systems to the specific needs of homeless persons. This article examines whether post-hospital discharge to a homeless medical respite program was associated with a reduced chance of 90-day readmission compared to other disposition options. Adjusting for imbalances in patient characteristics using propensity scores, respite patients were the only group that was significantly less likely to be readmitted within 90 days compared to those released to Own Care. Respite programs merit attention as a potentially efficacious service for homeless persons leaving the hospital.

Long-term housing and work outcomes among treated cocaine-dependent homeless persons.

Communities across the United States have initiated plans to end chronic homelessness. In many of these communities, addiction treatment programs remain the default point of entry to housing and services. This study examined the percentage of cocaine-using homeless persons (all with psychiatric distress) attaining stable housing and employment 12 months after entering a randomized trial of intensive behavioral day treatment, plus one of the following for 6 months: no housing; housing contingent on drug abstinence; housing not contingent on abstinence. Of 138 participants, the percentages with stable housing and employment at 12 months were 34.1 and 33.3%, respectively. Analyses suggested superior outcomes in trial arms that offered housing as part of the behavioral treatment. The majority of participants, however, did not achieve housing or employment, in part because of the limited capacity of the local housing programs to accommodate persons who had not achieved perfect abstinence. The findings demonstrate a helpful role for addiction treatment and suggest the need for services to support housing of persons who reduce but do not eliminate all substance use.

Need and non-need factors associated with addiction treatment utilization in a cohort of homeless and housed urban poor.

BACKGROUND: Research on addiction treatment utilization in indigent samples mainly has been retrospective, without measures of addictive consequences, social network influences, and motivation. Prospective assessment of factors influencing utilization could inform policy and clinical care. OBJECTIVE: We sought to identify factors associated with utilization of addiction treatment and mutual help groups among substance-dependent persons with high rates of homelessness. RESEARCH AND METHODS: This was a prospective cohort of patients detoxified from alcohol or drugs at baseline who were followed for 2 years in a randomized clinical trial of linkage to primary care (n = 274). Outcomes included utilization of Inpatient/Residential, Outpatient, Any Treatment, and Mutual Help Groups. Predictor variables in longitudinal regression analyses came from the literature and clinical experience, organized according to theoretical categories of Need, and non-Need (eg, Predisposing and Enabling). RESULTS: Many subjects used Inpatient/Residential (72%), Outpatient (62%), Any Treatment (88%) or Mutual Help Groups (93%) at least once. In multivariable analyses, addictive consequences (odds ratio [OR] 1.38, 95% confidence interval [CI] 1.12-1.71), motivation (OR 1.32, 95% CI 1.09-1.60), and female gender (OR 1.80, 95% CI 1.13-2.86) were associated with most treatment types (ORs are for Any Treatment). Homelessness was associated with Residential/Inpatient (for Chronically Homeless vs. Housed, OR 1.75, 95% CI 1.04-2.94). Living with one's children (OR 0.51, 95% CI 0.31-0.84) and substance-abusing social environment (OR 0.65, 95% CI 0.43-0.98) were negatively associated with Any Treatment. CONCLUSIONS: In this cohort of substance-dependent persons, addictive consequences, social network variables, and motivation were associated with treatment utilization. Non-need factors, including living with one's children and gender, also were significant.

Conformationally locked isostere of phosphoSer-cis-Pro inhibits Pin1 23-fold better than phosphoSer-trans-Pro isostere.

Stereoisomeric cis and trans substrate analogues for Pin1 were designed and synthesized. The central phosphoSer-Pro core of the Pin1 substrate was replaced by cis and trans amide isosteres in Ac-Phe-Phe-pSer-Psi[(Z and E)CH=C]-Pro-Arg-NH(2), 1 and 2, peptidomimetics. They were synthesized on solid phase in 17% yield for the cis analogue 1, and 16% yield for the trans analogue 2. A second trans amide isostere with a C-terminal N-methylamide 3 was synthesized in 7% yield. The protease-coupled Pin1 assay showed that all three compounds inhibited the Pin1 peptidyl-prolyl isomerase (PPIase) enzymatic activity. The cis isostere 1 was 23 times more potent (K(i) = 1.74 +/- 0.08 muM) than its trans counterpart 2 (K(i) = 40 +/- 2 muM) in competitive inhibition of Pin1. These results suggest that the catalytic site of Pin1 binds cis substrates more tightly in aqueous solution. Antiproliferative activity toward the A2780 human ovarian cancer cell line by the cis and trans analogues correlates with Pin1 inhibition results.