Alcohol mixed with energy drinks and aggressive behaviors in adolescents and young adults: A systematic review

PURPOSE

Consuming alcohol mixed with energy drinks (AmED) is a high-risk drinking practice. This systematic review examines how AmED use contributes to aggression (physical and sexual), in what role(s) (perpetrator and/or victim), in adolescents and young adult drinkers (age 25 and younger).

METHODS

Computer assisted search identified 844 studies conducted prior to March 2023; of them 17 met inclusion criteria.

RESULTS

AmED use was significantly associated with aggressive behaviors. Between-subject studies suggests that AmED consumers have higher rates of perpetration (physical fights, bullying) and victimization compared to peers who only drink alcohol; however, within-subject studies of AmED users find no difference in physical aggression by drinking event (AmED vs. occasions where consumer drinks alcohol only). Similarly, AmED use was a risk factor for sexually aggressive behaviors (e.g., unwanted contact) and victimization.

CONCLUSIONS

AmED use is a significant risk factor both victimization and perpetration of violent acts. Differences in within- versus between-study findings suggests that risk is associated with use of AmED, and not event level differences in drinking occasions among AmED users. Findings highlight the relative paucity of studies examining victimization and sexual violence and the need for future studies to incorporate more diverse samples and methodologies to better understand patterns of AmED use, perpetration, and victimization.

Experimental tasks of behavioral risk taking in alcohol administration studies: A systematic review

Research on emerging adults shows this population exhibits the highest rates of alcohol use and engages in the riskiest of behaviors (Boyer, 2006; Fromme, Corbin, & Kruse, 2008). Among experimental paradigms, prior reviews have established an increase in behavioral risk taking while under the influence of alcohol (Moskowitz & Robinson, 1988; Martin et al., 2013; Weafer & Fillmore, 2016). Previous research highlighted the importance of alcohol dose on behavioral risk taking and the lack of agreement on which psychometric tools are most accurate in assessing behavioral risk taking (Beulow & Blaine, 2015; King, Toule, De Wit, & Holdstock, 2002). This systematic review of experimental paradigms assessing the effects of the dose of alcohol on various behavioral risk taking tasks suggest that higher alcohol doses (0.6 g/kg and above) produces the most robust increase in behavioral risk taking across tasks, compared to lower doses of alcohol (<0.6 g/kg). Results suggest the BART is the most sensitive behavioral risk task used to detect increases in risk taking in moderate/higher doses compared to lower doses of alcohol. This review also highlights the difficulty in measuring behavioral risk taking, as behavioral risk taking is a complex, multifaceted phenomenon that may involve multiple constructs and means to capture it. Future research is needed to standardize experimental administration protocols, to aid in advancing the field of alcohol administration experiments, and to determine the most accurate measurement of behavioral risk taking. PUBLIC HEALTH SIGNIFICANCE: Past experimental paradigms measuring behavioral risk taking under the influence of alcohol in emerging adults have used various alcohol administration paradigms, experimental protocols, and behavioral risk tasks. Key to examining behavioral risk taking via experimental paradigms should use at higher alcohol doses. Future interventions need to assess for levels of blood alcohol concentration when assessing for at-risk populations for alchol use disorders.

Brain activation to cannabis- and alcohol-related words in alcohol use disorder

Cannabis abuse commonly co-occurs with alcohol use disorder (AUD). With increased acceptance and accessibility to cannabis in the US, it is imperative to understand the psychological and neural mechanisms of concurrent alcohol and cannabis use. We hypothesized that neural alcohol-cue conditioning may extent to other drug-related stimuli, such as cannabis, and underwrite the loss of control over reward-driven behavior. Task-activated fMRI examined the neural correlates of alcohol- and cannabis-related word cues in 21 abstinent AUD and 18 control subjects. Relative to controls, AUD showed behavioral attentional biases and frontal hypoactivation to both alcohol- and cannabis-related words. This cue-elicited prefrontal hypoactivation was related to higher lifetime alcohol consumption (pcorrected < 0.02) and modulated by past cannabis use histories (p ≦ 0.001). In particular, frontal hypoactivation to both alcohol and cannabis cues was pronounced in AUD without prior cannabis exposure. Overall, frontal control mechanisms in abstinent AUD were not sufficiently engaged to override automatic alcohol and cannabis-related intrusions, enhancing the risk for relapse and potentially for alcohol and cannabis co-use with the increased social acceptance and accessibility in the US.

Replication of factors related to blackout incidence in U.S. high school students: A brief report

Alcohol-related blackouts are a common, yet serious consequence that can result from heavy alcohol intake. This study tested a model examining whether factors identified in related samples (i.e., adolescents residing in the U.K. and U.S. college students) predicted blackouts in community-dwelling U.S. high school youth. Participants from a Northeastern U.S. high school with prior alcohol use (M_age = 16.0 years; 48.2% male, 78.0% White) completed a paper-and-pencil assessment including measures of demographics, alcohol and other substance use, externalizing behaviors, and injunctive norms about risky drinking behaviors. Hierarchical logistic regression examined which factors identified for U.K. residing adolescents (Block 1) replicated in the U.S. sample, and whether factors identified in samples of U.S. college students added additional explained variance (Block 2). Blackouts were reported by 35.6% of students. Regression results indicated that two variables previously identified in adolescents, female gender (OR = 3.26) and increased alcohol use (OR = 1.27) were associated with blackouts. College student risk factors of drinking game (DG) participation and, to a lesser degree injunctive norms for passing out, emerged as additional risk factors (ORs = 2.85 and 1.32, respectively), with the final model explaining 39% of the variance in blackouts. This study advances our understanding of blackouts in younger drinkers and identifies the importance of addressing blackouts within the context of intervention programming that addresses cognitions and high risk drinking practices like DGs.

Bell Ringers: Factors Related to Concussive Events in Children Playing Tackle Football

INTRODUCTION

Sports-related concussion is a significant pediatric health risk, given the number of children involved in sports and the vulnerability of developing brains. Although most research has focused on high school/college athletes, these findings may not be applicable to younger athletes.

METHOD

A mixed-methods analysis examined concussion incidence and sequelae in a cohort of 8- to 13-year-old males (N = 31) playing youth football and their parents. Parents provided background information and completed mood/behavioral questionnaires, and each athlete completed a neuropsychological battery.

RESULTS

Eight athletes (26%) had a history of concussion before assessment. Concussion risk was related to lack of medical evaluation in prior concussions, tackling exposure (in both offensive and defensive positions), and multisport participation. There were no cognitive or psychological differences based on concussion history.

DISCUSSION

Findings identify factors that may contribute to concussion risk in children and show the need for further research in this understudied population.

Impact of a University Alcohol Policy Change on Bystander Responses to Alcohol-Related Medical Emergencies

Two studies evaluated the implementation of a stricter campus underage drinking policy on service utilization and bystander helping behaviors for alcohol-related medical emergencies. A program evaluation (Study 1) examined campus emergency medical service logs assessing changes in call volume and service utilization, finding a 30% reduction in call volume postpolicy change. Study 2 provided a qualitative data summarizing campus first responder ( N =  35) accounts of off-duty alcohol-related emergency calls. Off-duty calls increased postpolicy change and thematic analyses indicated they were (a) motivated by fear of campus sanctions, (b) often yielded delays or failures to contact campus emergency staff, and (c) resulted from student misunderstandings of policy implications for bystander helpers. Findings highlight potential challenges in executing environmental strategies to reduce college drinking.

Evaluating the Effectiveness of a Medical Amnesty Policy Change on College Students' Alcohol Consumption, Physiological Consequences, and Helping Behaviors

OBJECTIVE

This study summarizes the association between medical amnesty policy (MAP) implementation and drinking behaviors at a 4-year university.

METHOD

First-year students (N = 1,246; 50.8% male) were assessed in the academic year pre- (2009-2010, n = 571) and post-implementation (2010-2011, n = 675). A cohort-sequential design was used. Students were assessed at college entry and end-of-year. Self-report measures assessed recent alcohol use, physiological consequences, and helping behaviors specific to alcohol-related medical emergencies.

RESULTS

MAP implementation did not increase drinking, overall consumption, or the incidence of physiological consequences. Modest increases in contacting residence life staff in the event of an emergency were also found.

CONCLUSIONS

This study provides empirical support that MAP policies do not increase consumption or problems and may reduce barriers to seeking help in the event of an emergency. Additional research is needed to establish the effectiveness of MAPs as an environmental-level strategy to reduce harmful drinking on campus.

Heterogeneity of Pregamers by Consumption and Reinforcement Reasons: A Latent Profile Analysis

BACKGROUND

Pregaming is a common, high-risk drinking activity among college students that has been largely unchangeable despite targeted intervention approaches. Therefore, identifying profiles of pregamers could enhance understanding of the risks associated with this practice and inform intervention development.

METHODS

This study identified subtypes of pregamers in undergraduates (N = 911; 60% female, 42.9% White) attending 3 U.S. universities in 2012. Self-report data assessed recent alcohol use (overall, heavy, and pregaming), pregaming motives, and demographics. Alcohol-related consequences were assessed via the Young Adult Alcohol Consequences Questionnaire.

RESULTS

Latent profile analysis using pregaming-specific indicators assessing motives (e.g., to avoid getting caught) and consumption (e.g., estimated pregaming blood alcohol concentration) yielded 5 unique profiles. Three profiles were characterized by pregaming on 50% or more of all drinking events that differed by pregaming consumption and motives: Instrumental (5.3%; heavy consumption, intoxication-driven motives), Global (16.0%; moderate consumption, indistinct motives), and Risk-averse (18.3%; moderate-to-heavy consumption, negatively reinforcing motives). Two profiles reported lower levels of pregaming: Occasional (32.4%; moderate consumption, indistinct motives) and Infrequent (28.0%; lowest pregaming involvement). Cross-profile differences were then examined for demographics, general drinking and pregaming-specific motives, and alcohol-related consequences. Profile comparisons indicated differences in overall alcohol consumption, ethnicity, gender, current living arrangements, Greek involvement, and a variety of alcohol-related consequences (ps < 0.01).

CONCLUSIONS

Overall, pregaming is a very heterogeneous behavior among college students in that some students utilize this drinking practice as a means to mitigate risk and others use it to promote intoxication. Results suggest that distinguishing pregamers by consumption as well as motives can facilitate the development of more tailored intervention approaches for students who engage in this high-risk practice.

Sex and Drugs and Starting School: Differences in Precollege Alcohol-Related Sexual Risk Taking by Gender and Recent Blackout Activity

Research has demonstrated a link between alcohol use and multiple forms of risky sexual behavior, particularly among college-age individuals. Studies have also linked heavy alcohol use to other problems, such as impaired consciousness resulting from an alcohol-induced blackout, which may impact sexual decision making. However, research has rarely examined sexual risk taking (SRT) in relation to blackouts, nor has it examined this construct during the precollege transition (i.e., the interval of time between high school graduation and college matriculation). This study examined the intersection between alcohol-involved SRT, blackouts, and gender in a sample of precollege individuals with prior alcohol use (N = 229; 54% male, 63% White). Results indicated that, despite drinking less per occasion, women reporting recent blackouts were at increased risk for experiencing unwanted, unsafe, and regretted sexual behaviors compared to men with recent blackouts and their peers with no recent blackouts. Women with recent blackouts also reported differences in alcohol expectancies that may increase their risk for experiencing negative consequences while drinking, including higher social expectancies and lower negative expectancies of danger. Future directions for research and implications for precollege interventions are discussed.

Variability in Pregaming Typologies Across the Freshman Year: A Multi-wave Latent Transition Analysis

BACKGROUND

Though research is rapidly expanding on pregaming and related risks, studies have not yet identified discrete subtypes of college pregamers or modeled how class membership changes across critical times like college entry.

OBJECTIVES

Latent Transition Analysis (LTA) identified classes of pregaming behaviors in entering college students and described transitions in latent statuses across the freshman year.

METHODS

Students with prior alcohol use (N = 711; 51.3% female; 63% White; Mage = 18) were surveyed at orientation and re-assessed at three follow-ups (Fall, Winter, and Spring). Items assessed overall drinking (past 30-day, number of binge episodes), pregaming (typical quantity, normativity relative to overall use, estimated pregaming BAC, drinks consumed post-pregaming event), and problems (overall and pregaming-specific).

RESULTS

LTA modeling yielded three distinct classes of pregaming membership (Low, Medium and High) that varied as a function of both overall use and pregaming practices. Evaluation of changes over the year indicated the greatest movement occurred immediately upon college entry, with significantly less movement was seen across the remainder of the year. Cross-class comparisons across all four time points showed clear differences in alcohol-related problems (overall as well as pregaming-specific), with students in the High class reporting markedly higher levels of problems on all domains.

CONCLUSIONS/IMPORTANCE

Overall, there appears to be considerable heterogeneity in pregaming behaviors, across both students and time that are directly related to differential levels of problems. Findings highlight the need to screen students early for risky drinking practices, including pregaming, and include pregaming-specific material in their campus screening and intervention programming.

Extreme Consumption Drinking Gaming and Prepartying Among High School Students

Drinking games and prepartying (i.e., drinking before going to a social gathering/event) have emerged as high-risk drinking behaviors in high school students. The present study examines the current prepartying behaviors of high school students who report current participation in extreme consumption games (e.g., Chugging) with those who do not. High school students (N=182) reporting current drinking games participation completed anonymous surveys. Gamers who prepartied frequently (vs. those who did not) were approximately 1.5 times more likely to play extreme consumption games, even after controlling for demographics, typical consumption, and participation in other types of drinking games. Practitioners should target adolescents who participate in extreme consumption games, particularly those who participate in this high-risk activity as a form of prepartying.

Identification of hazardous drinking with the Young Adult Alcohol Consequences Questionnaire: Relative operating characteristics as a function of gender

Heavy and problematic drinking is common on college campuses and is associated with myriad hazardous outcomes. The Young Adult Alcohol Consequences Questionnaire (YAACQ; Read et al., 2006) was developed to provide comprehensive and expedient assessment of negative consequences of young adult drinking and has been used in a number of research and clinical settings. To date, no empirically derived cutoffs for the YAACQ have been available for use in the identification of those drinkers at greatest risk. This was the objective of the present study. In a large (N = 1,311) and demographically heterogeneous multisite sample, we identified cutoff scores for the YAACQ, and the contrasted detection of hazardous drinking using these cutoffs with those recommended for the Alcohol Use Disorders Identification Test (AUDIT). We also examined whether cutoffs differed by gender. Results of receiver operating characteristic (ROC) analysis yielded cutoffs that delineate 3 levels (or zones) of hazardous drinking risk: low, moderate, and high. A cutoff of 8 differentiated those at low risk from those at moderate risk or greater, and a cutoff of 16 differentiated between moderate and high risk. These zones corresponded to other indices of risky drinking, including heavy episodic "binge" drinking, more frequent alcohol consumption, and engagement in alcohol risk behaviors. Scores differentiating low to moderate risk differed for men (8) and women (10), whereas the cutoff for high risk was the same (16) across the sexes. Findings suggest that the YAACQ can be used to reliably assess level of drinking risk among college students. Furthermore, these cut scores may be used to refer to interventions varying in intensity level, based on level of indicated alcohol risk. (PsycINFO Database Record

Identifying classes of conjoint alcohol and marijuana use in entering freshmen

The current study identified classes of conjoint marijuana and alcohol use in entering college freshmen using latent profile analysis (N = 772; 53% male, 60% White; Mage = 18). Results yielded 4 distinct groups: Class 1 (moderate drinking with recent marijuana use: 22% of sample), Class 2 (moderate drinking with no recent marijuana use: 25%), Class 3 (light drinking with no recent marijuana use: 40%) and Class 4 (heavy drinking with recent marijuana use: 14%). Separate pairwise contrasts examined cross-class differences in demographics and drinking behaviors, comparing differences in drinking when current marijuana use was controlled (Class 1 vs. 4) and differences in marijuana use when drinking was held relatively constant (Class 1 vs. 2). Among moderate drinkers, recent marijuana users were more likely to drink more than intended, drink to get drunk, and had more problems (including higher rates of blackouts, physical injury, and DUI) relative to peers who refrained from marijuana. No cross-class differences were found for alcohol expectancies or behavioral motives. Findings from these analyses show the presence of distinct groups of conjoint users with different drinking behaviors and consequence profiles, and suggest that conjoint alcohol-marijuana use may be more problematic overall than single substance involvement and highlight the need for developing campus prevention and intervention programs that address the increased risk from polysubstance involvement.

Trouble brewing: pregaming among high school and incoming college students

Pregaming (a.k.a., "prepartying," "pre-funking," or "predrinking") consists of drinking before going to a social function or gathering where alcohol may or may not be served. Existing research suggests that pregaming in high school and pre-college (i.e., the period between high school graduation and the start of college) is widespread. Moreover, pregaming prevalence appears to rapidly increase after students graduate from high school and transition into college. Thus, the purpose of this brief review is threefold: (a) to summarize the existing (albeit limited) research on pregaming among high school students and incoming college freshmen, (b) to present an overview of the risk factors that have been identified for participation in pregaming, and (c) to discuss the implications for practice that may be particularly relevant for school-employed/affiliated nurses as well as health practitioners who work in college settings.

Getting "game": pregaming changes during the first weeks of college

OBJECTIVE

Many students pregame (ie, drink before drinking), but there are scant data evaluating changes following college entry. The authors examined pregaming across the fall quarter and identified predictors of change and initiation in college.

PARTICIPANTS

Freshmen (N = 708; 53% female, 100% drinkers) were recruited during university orientation (baseline).

METHODS

Self-report data were collected at baseline and end of fall quarter for 3 cohorts (the 2008-2010 academic years) and included demographics, alcohol use, problems, pregaming, personality, and expectancies.

RESULTS

Pregaming increased from 61.7% (baseline) to 79.9% (follow-up), with students pregaming twice as often and attaining higher blood alcohol concentration at follow-up. Many (54%) baseline non-pregamers initiated by follow-up. Initiation was associated with increased overall drinking (including heavy episodic drinking), positive expectancies, and greater behavioral activation sensitivity.

CONCLUSIONS

Pregaming rapidly escalates upon college entry and students who initiate in college may be at higher risk for alcohol-related problems. Campus prevention and intervention efforts should consider including pregaming in their prevention programming.

PARP-1 deficiency blocks IL-5 expression through calpain-dependent degradation of STAT-6 in a murine asthma model

BACKGROUND

We recently showed that poly(ADP-ribose)polymerase-1 (PARP-1) may play a role in allergen (ovalbumin)-induced airway eosinophilia, potentially through a specific effect on IL-5 production. We also reported that while IL-5 replenishment promotes reversal of eosinophilia in lungs of PARP-1(-/-) mice, IL-4 or Immunoglobulin E replenishment do not, suggesting a potentially significant regulatory relationship between PARP-1 and IL-5.

OBJECTIVE

To explore the mechanism by which PARP-1 regulates IL-5 production and to determine how PARP-1 inhibition blocks allergen-induced eosinophilia.

METHODS

This study was conducted using a murine model of allergic airway inflammation and primary splenocytes.

RESULTS

PARP-1 knockout-associated reduction in IL-5 upon allergen exposure occurs at the mRNA level. Such an effect appears to take place after IL-4 receptor activation as PARP-1 inhibition exerted no effect on JAK1/JAK3 activation. Signal transducer and activator of transcription-6 (STAT-6) protein was severely downregulated in spleens of PARP-1(-/-) mice without any effect on mRNA levels, suggesting an effect on protein integrity rather than gene transcription. Interestingly, the degradation of STAT-6 in PARP-1(-/-) mice required allergen stimulation. Additionally, PARP-1 enzymatic activity appears to be required for STAT-6 integrity. The downregulation of STAT-6 coincided with mRNA and protein reduction of GATA-binding protein-3 and occupancy of its binding site on the IL-5 gene promoter. IL-4 was sufficient to induce STAT-6 downregulation in both PARP-1(-/-) mice and isolated splenocytes. Such degradation may be mediated by calpain, but not by proteasomes.

CONCLUSION

These results demonstrate a novel function of PARP-1 in regulating IL-5 expression during allergen-induced inflammation and explain the underlying mechanism by which PARP-1 inhibition results in IL-5 reduction.

Cigarette smoking in opioid-using patients presenting for hospital-based medical services

Little is known about cigarette smoking among opioid users who are not in substance abuse treatment. The study examined cigarette smoking in out-of-treatment opioid users presenting at a hospital who participated in drug abuse research. Participants exhibited a high rate of smoking (92%) at baseline that remained unchanged at one year and were moderately nicotine-dependent. Nineteen percent preferred unfiltered cigarettes. Women were more likely to smoke menthol cigarettes; men were more likely to smoke unfiltered cigarettes. Caucasians tended to smoke more than other ethnicities and exhibited greater dependence. Out-of-treatment drug users continue to be at high risk for continued smoking.

The relationship between smoking history and current functioning in disabled community-living older adults

PURPOSE

This study was conducted to determine characteristics associated with continued cigarette use in frail older adults and to examine how smoking history relates to current psychiatric, cognitive, and occupational functioning.

METHODS

Archival records were gathered for 1,064 patients (69% women) who entered On Lok SeniorHealth Services between January 1996 and December 2000. Participants were interviewed on program entry and assessed for smoking history, depressive symptoms, affective disorders, cognitive functioning, alcohol use, and physical functioning (activities of daily living [ADLs] and instrumental ADLs). Cross-sectional analyses were conducted to examine functioning at enrollment relative to smoking history.

RESULTS

Smoking history was related to age at program entry, with current smokers entering On Lok at an earlier age than former or never smokers. Current smokers were more likely to be male, to be of Caucasian or African American descent, to consume alcohol on a regular basis, and to be more independent on ADLs. Specifically, they were more independent on tasks related to their capacity to procure cigarettes or continue smoking, including shopping, using transportation, managing money, dressing themselves, and walking. Smoking history was related to depression, with symptoms lower for current and former smokers.

CONCLUSIONS

Current smokers present for services at an earlier age and have higher levels of independence on ADLs instrumental to nicotine use. Data indicate characteristics associated with continued smoking and provide a foundation for targeting older individuals for cessation efforts.

Influences of Mood, Depression History, and Treatment Modality on Outcomes in Smoking Cessation

The relationship between major depressive disorder (MDD), treatment modality, and mood was evaluated in smokers participating in cessation programs. Participants (N = 549, 53.7% women, 46.3% men, 28% endorsing past MDD episodes) were randomly assigned to a cognitive-behavioral treatment (CBT) or health education (HE) intervention. Participants with a history of recurrent MDD (MDD-R) had higher rates of abstinence in CBT compared with HE even when the contribution of mood and the interaction between mood and an MDD x Treatment variable were included in the model. Likewise, higher levels of mood disturbance were reported by MDD-R smokers compared with those reporting a single episode. The study replicated results reported by R. A. Brown et al. (2001) and expanded upon them by evaluating the differential contribution of poor mood on cessation outcomes relative to MDD history.

Pregnancy and interferon-tau upregulate gene expression of members of the 1-8 family in the bovine uterus

The 1-8 family (1-8U, 1-8D, Leu-13/9-27) of interferon (IFN)-inducible genes encodes proteins that are components of multimeric complexes involved with transduction of antiproliferative and homotypic adhesion signals. Human 1-8 family members are highly similar and are regulated by type 1 and type 2 IFNs. Because the bovine uterus is bathed in conceptus-derived IFN tau during early pregnancy, it was hypothesized that members of the 1-8 family were upregulated in the bovine uterus during early pregnancy. Oligonucleotide primers were designed based on human and rat 1-8U and Leu-13 cDNAs and used in reverse transcription polymerase chain reactions to amplify bovine cDNAs from endometrial RNA. The bovine 1-8U cDNA was sequenced, found to be 84% identical to the human 1-8U, and used to screen a bovine endometrial cDNA library to isolate the full-length 1-8U and Leu-13 cDNAs. The inferred amino acid sequences of bovine 1-8U and Leu-13 were 72% and 73% identical to their respective human counterparts. Bovine 1-8U and Leu-13 retain an amino acid motif that is conserved in other 1-8 family members and in some ubiquitin-conjugating enzymes (E2s). This motif is critical for function of E2s in covalently linking ubiquitin to targeted proteins. Northern blotting revealed that bovine endometrial 1-8U and Leu-13 mRNAs were upregulated on Day 15 of pregnancy (P < 0.0001) and continued to accumulate through Day 18 of pregnancy (P < 0.05) when compared with endometrium from nonpregnant cows. The bovine 1-8U and Leu-13 mRNAs were also upregulated (P < 0.05) by IFN tau (25 nM) within 3 h, continued to accumulate through 12 h, and reached a plateau at 12-24 h in cultured bovine endometrial cells. In situ hybridization revealed that mRNAs encoding 1-8 family members were heavily localized to glandular epithelium but also were present to a lesser extent in the luminal epithelium and stroma. The temporal upregulation of 1-8U and Leu-13 mRNAs by pregnancy and IFN tau and tissue distribution of these mRNAs paralleled closely that of the ubiquitin homolog, IFN-stimulated gene product 17. These IFN-induced proteins probably work together to prepare the endometrium for adhesion of the developing conceptus.

Kinetic analysis of the conjugation of ubiquitin to picornavirus 3C proteases catalyzed by the mammalian ubiquitin-protein ligase E3alpha

The 3C proteases of the encephalomyocarditis virus and the hepatitis A virus are both type III substrates for the mammalian ubiquitin-protein ligase E3alpha. The conjugation of ubiquitin to these proteins requires internal ten-amino acid-long protein destruction signal sequences. To evaluate how these destruction signals modulate interactions that must occur between E3alpha and the 3C proteases, we have kinetically analyzed the formation of ubiquitin-3C protease conjugates in a reconstituted system of purified E1, HsUbc2b/E2(14Kb), and human E3alpha. Our measurements show that the encephalomyocarditis virus 3C protease is ubiquitinated in this system with K(m) = 42 +/- 11 microm and V(max) = 0.051 +/- 0.01 pmol/min whereas the parameters for the ubiquitination of the hepatitis A virus 3C protease are K(m) = 20 +/- 5 microm and V(max) = 0.018 +/- 0.003 pmol/min. Mutations in the destruction signal sequences resulted in changes in the rate at which E3alpha conjugates ubiquitin to the altered 3C protease proteins. The K(m) and V(max) values for these reactions change proportionally in the same direction. These results suggest differences in rates of conjugation of ubiquitin to 3C proteases are primarily a k(cat) effect. Replacing specific encephalomyocarditis virus 3C protease lysine residues with arginine residues was found to increase, rather than decrease, the rate of ubiquitin conjugation, and the K(m) and V(max) values for these reactions are both higher than for the wild type protein. The ability of E3alpha to catalyze the conjugation of ubiquitin to both 3C proteases was found to be inhibited by lysylalanine and phenylalanylalanine, demonstrating that the same sites on E3alpha that bind destabilizing N-terminal amino acids in type I and II substrates also interact with the 3C proteases.

N-end rule specificity within the ubiquitin/proteasome pathway is not an affinity effect

The N-end rule relates the amino terminus to the rate of degradation through the ubiquitin/26 S proteasome pathway. Proteins bearing basic (type 1) or large hydrophobic (type 2) amino termini are assumed to be targeted through this pathway by their higher affinity for binding to the responsible E3 ligase compared with proteins bearing other residues (type 3). Paradoxically, a significant fraction of eukaryotic protein degradation occurs through the N-end rule pathway, although the majority of cellular proteins are type 3 substrates. We have exploited specific interactions between ubiquitin carrier proteins (E2/Ubc) and their cognate E3 ligases to purify for the first time the mammalian N-end rule ligase E3alpha/Ubr1 to near homogeneity. In vitro studies show that E3alpha forms lysine 48-linked polyubiquitin degradation signals on type 1-3 substrates and is absolutely dependent on Ubc2/Rad6 orthologs. Biochemically defined kinetic studies show that the basis of N-end rule specificity is a k(cat) rather than the K(m) effect originally proposed, since all three substrate classes show similar binding affinities (K(m) approximately 5 microm) but V(max) values that are 100- and 50-fold greater for type 1 and 2 versus type 3 model substrates, respectively. In addition, the N-end rule dipeptides lysylalanine and phenylalanylalanine are general noncompetitive inhibitors for E3alpha-catalyzed ubiquitination of type 1-3 substrates rather than type-specific competitive inhibitors as predicted. These observations are consistent with a model in which the N-end rule effect reflects substrate binding-induced transitions in E3alpha to a catalytically competent conformer, the equilibrium for which depends on the identity of the amino terminus or the presence of basic or hydrophobic surface features. The model reconciles conflicts between specific predictions and empirical observations relating N-end rule targeting in addition to explicating the efficacy of selected dipeptides as potent in vivo inhibitors of this pathway.

Development of substance abuse problems among drug-involved offenders. Evidence for the telescoping effect

PURPOSE

The present study was designed to evaluate gender differences in the development of substance abuse disorders among drug-involved offenders and to determine whether women in this population exhibit a telescoping effect (i.e., acceleration in the progression from substance use to substance abuse), which has been observed in other setting.

METHOD

Participants consisted of 160 polysubstance-abusing individuals (118 men, 42 women) who were admitted to two Florida drug court programs. Data were obtained from the Addiction Severity Index, intake interviews, and archival court records.

RESULTS

Female and male offenders differed significantly in the developmental trajectory of their addiction. Women offenders initiated alcohol and marijuana use significantly later in life than their male cohorts but began using cocaine earlier in the course of their addiction. Women also reported more problems related to cocaine use and significantly more prior treatment episodes. Women were found to have a shorter latency from first use of cocaine to cocaine abuse. Findings are consistent with those of previous studies examining gender differences among individuals referred for substance abuse treatment. Future directions for research and implications for treatment planning are discussed.

Variations in site and levels of expression of chondrocyte nucleotide pyrophosphohydrolase with aging

The aim of this study was to identify changes in cartilage intermediate layer protein/nucleotide pyrophosphohydrolase (CILP/NTPPH) expression in articular cartilage during aging. Adult (3-4 years old) and young (7-10 days old) porcine articular hyaline cartilage and fibrocartilage were studied by Northern blot analysis, in situ hybridization, and immunohistochemistry using a complementary DNA (cDNA) probe encoding porcine CILP/NTPPH and antibody to a synthetic peptide corresponding to a CILP/NTPPH sequence. Northern blot analysis of chondrocytes showed lower expression of CILP/NTPPH messenger RNA (mRNA) in young cartilage than in adult cartilage. In adult cartilage, extracellular matrix from the surface to the middeep zone was immunoreactive for CILP/NTPPH, especially in the pericellular matrix surrounding the middeep zone chondrocytes. In young cartilage, chondrocytes were moderately immunoreactive for CILP/NTPPH throughout all zones except the calcified zone. The matrix of young cartilage was negative except in the superficial zone. In young cartilage, CILP/NTPPH mRNA expression was undetectable. In adult cartilage, chondrocytes showed strong mRNA expression for CILP/NTPPH throughout middeep zones. Protein and mRNA signals were not detectable below the tidemark. CILP/NTPPH secretion into matrix around chondrocytes increases with aging. In this extracellular site it may generate inorganic pyrophosphate and contribute to age-related calcium pyrophosphate dihydrate crystal deposition disease.

Novel mechanism of surface catalysis of protein adduct formation. NMR studies of the acetylation of ubiquitin

Reactivity of surface lysyl residues of proteins with a broad range of chemical agents has been proposed to be dependent on the catalytic microenvironment of the residue. We have investigated the acetylation of wild type ubiquitin and of the UbH68N mutant to evaluate the potential contribution of His-68 to the reactivity of Lys-6, which is about 4 A distant. These studies were performed using [1-(13)C]acetyl salicylate or [1,1'-(13)C(2)]acetic anhydride, and the acetylated products were detected by two-dimensional heteronuclear multiple quantum coherence spectroscopy. The results demonstrate that His-68 makes a positive contribution to the rate of acetylation of Lys-6 by labeled aspirin. Additionally, a pair of transient resonances is observed after treatment of wild type ubiquitin with the labeled acetic anhydride but not upon treatment of the H68N mutant. These resonances are assigned to the acetylated His-68 residue. The loss of intensity of the acetylhistidine resonances is accompanied by an increase in intensity of the acetyl-Lys-6 peak, supporting the existence of a transacetylation process between the acetylhistidine 68 and lysine 6 residues located on the protein surface. Hence, this may be the first direct demonstration of a catalytic intermediate forming on the protein surface.

Ubiquitination and degradation of the zebrafish paired-like homeobox protein VSX-1

Vsx-1 is a paired-like : CVC homeobox protein dynamically expressed during zebrafish development. Previous results indicate that Vsx-1 influences bipolar cell differentiation and maintenance of these cells in the adult retina. To understand the developmental regulation of this transcription factor, we investigated ubiquitination as a possible posttranslational mechanism. In vitro, Vsx-1 was conjugated with multiple ubiquitin moieties. Proteasome inhibitors and added ubiquitin increased the accumulation of Vsx-1-ubiquitin(n) complexes and stabilized unmodified Vsx-1. Also, in transiently transfected COS-7 cells, Vsx-1 is ubiquitinated, and pulse-chase experiments show that Vsx-1 proteolysis occurs. Vsx-1 proteins with C-terminal deletions retained the capacity for initial modification by ubiquitin but lost the capacity for efficient chain elongation. These results show that Vsx-1 is a substrate of the ubiquitin/proteasome pathway and suggest that C-terminal sequences of Vsx-1 are critical for ubiquitin chain elongation. In addition, our findings suggest that ubiquitin-dependent proteolysis regulates Vsx-1 during zebrafish retinal development.

Identification of a novel SCAN box-related protein that interacts with MZF1B. The leucine-rich SCAN box mediates hetero- and homoprotein associations

The SCAN box or leucine-rich (LeR) domain is a conserved motif found within a subfamily of C(2)H(2) zinc finger proteins. The function of a SCAN box is unknown, but it is predicted to form alpha-helices that may be involved in protein-protein interactions. Myeloid zinc finger gene-1B (MZF1B) is an alternatively spliced human cDNA isoform of the zinc finger transcription factor, MZF1. MZF1 and MZF1B contain 13 C(2)H(2) zinc finger motifs, but only MZF1B contains an amino-terminal SCAN box. A bone marrow cDNA library was screened for proteins interacting with the MZF1B SCAN box domain and RAZ1 (SCAN-related protein associated with MZF1B) was identified. RAZ1 is a novel cDNA that encodes a SCAN-related domain and arginine-rich region but no zinc finger motifs. Co-immunoprecipitation assays demonstrate that the SCAN box domain of MZF1B is necessary for association with RAZ1. By yeast two-hybrid analysis, the carboxyl terminus of RAZ1 is sufficient for interaction with the MZF1B SCAN box. Furthermore, MZF1B and RAZ1 each self-associate in vitro via a SCAN box-dependent mechanism. These data provide evidence that the SCAN box is a protein interaction domain that mediates both hetero- and homoprotein associations.

The binding site for UCH-L3 on ubiquitin: mutagenesis and NMR studies on the complex between ubiquitin and UCH-L3

The ubiquitin fold is a versatile and widely used targeting signal that is added post-translationally to a variety of proteins. Covalent attachment of one or more ubiquitin domains results in localization of the target protein to the proteasome, the nucleus, the cytoskeleton or the endocytotic machinery. Recognition of the ubiquitin domain by a variety of enzymes and receptors is vital to the targeting function of ubiquitin. Several parallel pathways exist and these must be able to distinguish among ubiquitin, several different types of polymeric ubiquitin, and the various ubiquitin-like domains. Here we report the first molecular description of the binding site on ubiquitin for ubiquitin C-terminal hydrolase L3 (UCH-L3). The site on ubiquitin was experimentally determined using solution NMR, and site-directed mutagenesis. The site on UCH-L3 was modeled based on X-ray crystallography, multiple sequence alignments, and computer-aided docking. Basic residues located on ubiquitin (K6, K11, R72, and R74) are postulated to contact acidic residues on UCH-L3 (E10, E14, D33, E219). These putative interactions are testable and fully explain the selectivity of ubiquitin domain binding to this enzyme.

Precursor processing of pro-ISG15/UCRP, an interferon-beta-induced ubiquitin-like protein

Induction of the 17-kDa ubiquitin-like protein ISG15/UCRP and its subsequent conjugation to cellular targets is the earliest response to type I interferons. The polypeptide is synthesized as a precursor containing a carboxyl-terminal extension whose correct processing is required for subsequent ligation of the exposed mature carboxyl terminus. Recombinant pro-ISG15 is processed in extracts of human lung fibroblasts by a constitutive 100-kDa enzyme whose activity is unaffected by type I interferon stimulation. The processing enzyme has been purified to apparent homogeneity by a combination of ion exchange and hydrophobic chromatography and found to be stimulated 12-fold by micromolar concentrations of ubiquitin. Analysis of the products of pro-ISG15 processing enzyme demonstrates specific cleavage exclusively at the Gly(157)-Gly(158) peptide bond to generate a mature ISG15 carboxyl terminus. Irreversible inhibition of pro-ISG15 processing activity by thiol-specific alkylating agents and a pH rate dependence conforming to titration of a single group of pK(a) 8.1 indicate the 100-kDa enzyme is a thiol protease. Partial sequencing of a trypsin-derived peptide indicates the enzyme is either the human ortholog of yeast Ubp1 or a Ubp1-related protein. As yeast do not contain ISG15, these results suggest that a ubiquitin-specific enzyme was recruited for pro-ISG15/UCRP processing by adaptive divergence.

An NMR analysis of the reaction of ubiquitin with [acetyl-1-13C]aspirin

The acetylation of ubiquitin by [acetyl-1-13C]aspirin has been studied using 2D NMR methods. Studies performed in a 50:50 H2O:D2O medium show doubling of the acetyl carbonyl resonances, indicating that all of the stable adducts formed involved amide linkages. Assignment of the heteronuclear multiple quantum coherence (HMQC) resonances was accomplished based on comparison of resonance intensities with the results of an Edman degradation analysis, pH titration studies of acetylated ubiquitin, and analysis of two ubiquitin mutants, K33R and K63R. The presence of a single tyrosine residue in close proximity to lysine-48 suggested another assignment strategy. Nitration of tyrosine-59 resulted in a small, pH-dependent shift of the resonance assigned to lysine-48, with a pK of 7.0, close to that expected for the nitrotyrosyl hydroxyl group. An additional adduct resonance with very low intensity also was observed and tentatively assigned to the acetylated N-terminal methionine residue. The relative rates of acetylation of the various lysine residues were obtained from time-dependent HMQC studies. Since no sample preparation artifacts were introduced, the levels of modification of the various residues could be determined with relatively high accuracy. Based on the time-dependent intensity data, the relative rate constants for modification of K6, K48, K63, K11, K33, and M1 were 1.0, 0.59, 0.43, 0.26, 0.23, and 0.03, respectively. These results were in much better agreement with amino accessibility predictions based on the crystal structure of the ubiquitin monomer than with predictions based on the ubiquitin structure in the crystallized dimeric and tetrameric forms. This approach provides a useful basis for understanding how local environmental factors can influence protein adduct formation, as well as for comparing the extent and specificity of various acetylation reagents.

Neurite outgrowth in PC12 cells. Distinguishing the roles of ubiquitylation and ubiquitin-dependent proteolysis

Nerve growth factor (NGF)-induced neurite outgrowth from rat PC12 cells was coincident with elevated (>/=2-fold) levels of endogenous ubiquitin (Ub) protein conjugates, elevated rates of formation of 125I-labeled Ub approximately E1 (Ub-activating enzyme) thiol esters and 125I-labeled Ub approximately E2 (Ub carrier protein) thiol esters in vitro, and enhanced capacity to synthesize 125I-labeled Ub-protein conjugates de novo. Activities of at least four E2s were increased in NGF-treated cells, including E2(14K), a component of the N-end rule pathway. Ubiquitylation of 125 I-labeled beta-lactoglobulin was up to 4-fold greater in supernatants from NGF-treated cells versus untreated cells and was selectively inhibited by the dipeptide Leu-Ala, an inhibitor of Ub isopeptide ligase (E3). However, Ub-dependent proteolysis of 125I-labeled beta-lactoglobulin was not increased in supernatants from NGF-treated cells, suggesting that neurite outgrowth is promoted by enhanced rates of synthesis (rather than degradation) of Ub-protein conjugates. Consistent with this observation, neurite outgrowth was induced by proteasome inhibitors (lactacystin and clasto-lactacystin beta-lactone) and was associated with elevated levels of ubiquitylated protein and stabilization of the Ub-dependent substrate, p53. Lactacystin-induced neurite outgrowth was blocked by the dipeptide Leu-Ala (2 mM) but not by His-Ala. These data 1) demonstrate that the enhanced pool of ubiquitylated protein observed during neuritogenesis in PC12 cells reflects coordinated up-regulation of Ub-conjugating activity, 2) suggest that Ub-dependent proteolysis is a negative regulator of neurite outgrowth in vitro, and 3) support a role for E2(14K)/E3-mediated protein ubiquitylation in PC12 cell neurite outgrowth.

Serum nucleotide pyrophosphohydrolase activity; elevated levels in osteoarthritis, calcium pyrophosphate crystal deposition disease, scleroderma, and fibromyalgia

OBJECTIVE

Quantification of serum nucleotide pyrophosphohydrolase (NTPPHase) activity in healthy subjects and in patients with various rheumatic diseases or with quad/hemiplegia, hemodialysis, or renal transplant.

METHODS

Colorimetric assay of enzyme activity in serum.

RESULTS

Serum NTPPHase activity in 85 healthy subjects was independent of age or sex and was highly reproducible in each individual. The biologic and methodologic coefficients of variation were nearly identical. Elevated enzyme levels were found in sera from patients with osteoarthritis/spondylosis, calcium pyrophosphate dihydrate (CPPD) crystal deposition, scleroderma, fibromyalgia, or hemodialysis. Renal transplant patients receiving cyclosporine had the highest enzyme activity of any group, whereas transplant patients not taking this drug had normal levels. Histograms of values in all groups showed a normal distribution.

CONCLUSION

Serum NTPPHase activity levels were significantly elevated in patients with degenerative arthritis whether or not CPPD crystals were present, in patients with either scleroderma or fibromyalgia, and in patients receiving hemodialysis therapy or taking cyclosporine.

Defects in the ubiquitin pathway induce caspase-independent apoptosis blocked by Bcl-2

Apoptosis requires the activation of caspases (formerly interleukin 1beta-converting enzyme-like proteases), in particular those related to the caspase-3/7/6 subfamily. Recent data, however, revealed that, although caspase-specific inhibitors delay apoptosis, they are often incapable of preventing it. To obtain evidence for caspase-independent steps of apoptosis, we artificially created a high amount of short-lived or aberrant proteins by blocking the ubiquitin degradation pathway. A temperature-sensitive defect in the ubiquitin-activating enzyme E1 induced apoptosis independent of the activation of caspase-3 and -6 and the cleavage of their respective substrates poly(ADP-ribose) polymerase and lamin A. In addition, neither the caspase 3/7-specific inhibitor N-benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethylketone nor the general caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone were capable of blocking this type of cell death. By contrast, Bcl-2 overexpression effectively protected cells from apoptosis induced by a defect in the E1 enzyme at the nonpermissive temperature. Bcl-2 acted downstream of the accumulation of short-lived or aberrant proteins because it did not prevent the overexpression of the short-lived proteins p53, p27(kip1), and cyclins D1 and B1 under conditions of decreased ubiquitination. These results suggest the existence of short-lived proteins that may serve the role of caspase-independent effectors of apoptosis and attractive targets of the death-protective action of Bcl-2.

Pathways of ubiquitin conjugation

The covalent attachment of the polypeptide ubiquitin to proteins marks them for degradation by the ubiquitin/26S proteasome-dependent degradation pathway. This pathway functions in regulating many fundamental processes required for cell viability. Phylogenetic analysis of ubiquitin sequences reveals greater variability among lower eukaryotes and defines essential residues, many of which are conserved among the three ubiquitin-like proteins known to undergo parallel ligation pathways. The hierarchical design of the ubiquitin conjugation mechanism provides great flexibility for the divergent evolution of new functions mediated by this posttranslational modification. Within this hierarchy, a single ubiquitin-activating enzyme provides charged intermediates to multiple targeting pathways defined by cognate ubiquitin carrier protein (E2)/ligase (E3) pairs. Sequence analysis of E2 isozymes shows that the E2 superfamily is composed of distinct function-specific families. The apparent lack of E2/E3 specificity suggested in the literature results from the presence of multiple isozymes within many E2 families and erroneous family assignments based on incomplete data sets. Other apparent inconsistencies are explained by interfamily sequence relationships among some E2 isoforms.

Molecular cloning and expression of a porcine chondrocyte nucleotide pyrophosphohydrolase

The porcine 127-kDa nucleotide pyrophosphohydrolase (NTPPHase) had been previously purified from the conditioned culture media of porcine articular cartilage. Protein sequencing of an internal 61-kDa proteolytic fragment of NTPPHase (61-kDa NTPPHase) determined the 26 N-terminal amino acids. This sequence was used to amplify a DNA fragment, which was used as a probe to clone the gene encoding the 61-kDa NTPPHase from a porcine chondrocyte cDNA library. DNA sequence analysis showed the cDNA insert to be 2509 bp, corresponding to a predicted open reading frame (ORF) encoding 599 amino acids. The 26 N-terminal amino acids of the 61-kDa NTPPHase were located within the ORF immediately downstream of a putative protease recognition region, RRKRR. This is consistent with this cDNA insert representing an internal proteolytic fragment of the full length 127-kDa NTPPHase. BLAST and FASTA analysis confirmed that the deduced amino acid sequence of 61-kDa NTPPHase was unique and did not possess a high degree of homology to sequence in the non-redundant protein and nucleotide databases. Proteins that possess limited homology (< 17%) with the 61-kDa NTTPPHase include several prokaryotic and eukaryotic ATP pyrophosphate-lyases (adenylate cyclase). Northern blot analysis of porcine chondrocyte RNA showed that the DNA encoding the 61-kDa NTPPHase hybridized to a single 4.0-kb RNA transcript. This DNA probe also hybridized to a single species of human chondrocyte RNA. Expression of a 61-kDa protein was detected by coupled in-vitro transcription/translation. Western blot analysis of this in-vitro transcription/translation reaction detected a 61-kDa protein, using an antibody raised against the peptide sequence that was originally used to clone the 61-kDa NTPPHase. These data indicate the successful in-vitro cloning and expression of the porcine chondrocyte 61-kDa NTPPHase. Future studies that utilize the gene encoding the 61-kDa NTPPHase may allow the characterization of the role of NTPPHase in calcium pyrophosphate dihydrate (CPPD) crystal deposition disease.

Evaluation of the susceptibility of the 3C proteases of hepatitis A virus and poliovirus to degradation by the ubiquitin-mediated proteolytic system

The picornavirus 3C proteases are required for the processing of viral polyproteins during infections of host cells. Here we report that the 3C protease of the hepatitis A virus, like that of the encephalomyocarditis virus, is a substrate for rapid, ubiquitin-mediated degradation in vitro. Ubiquitin was shown to stimulate the turnover of the hepatitis virus 3C protease, and labeled protease was found to become incorporated into a mixture of high molecular weight species, which is characteristic of conjugation with polyubiquitin chains. In the presence of methylated ubiquitin, a new 33 kDa species formed, consistent with the generation of a monoubiquitin-3C protease conjugate. The rate of degradation of the 3C protease was reduced by inhibitors of the 26S proteasome. A similar evaluation of the 3C protease of poliovirus revealed that it is stable protein and is not conjugated with ubiquitin. It was also determined that the hepatitis A and encephalomyocarditis virus 3C proteases compete with each other for conjugation with ubiquitin and for degradation. This suggests that the two 3C proteases are both recognized by the same ubiquitin system enzyme, or enzymes, responsible for selecting them as targets for destruction.

Nucleotide pyrophosphohydrolase in human synovial fluid

OBJECTIVE

To identify the molecular forms of ectonucleotide pyrophosphohydrolase (NTPPHase) in human synovial fluid (SF).

METHODS

We examined synovial fluids from 32 patients with various joint diseases [10 calcium pyrophosphate dihydrate (CPPD) deposition disease; 7 osteoarthritis (OA); 6 rheumatoid arthritis (RA); 3 after total knee arthroplasty (TKA); 6 olecranon bursa] and 3 normal joint fluids. Joint fluids were analyzed after sequential centrifugation for NTPPHase activity and by Western blot using polyclonal antibodies against 127 kDa porcine articular cartilage vesicle-associated NTPPHase and against PC-1 and 58 kDa, 2 other ecto-NTPPHases. Lysate from human synoviocytes, porcine chondrocytes, and their conditioned media were examined using antibodies to these ecto-NTPPHases. Radiographs of joints from which fluid was obtained were graded for degenerative changes 0-4 using a standard method.

RESULTS

NTPPHase activity was found in all pathological and normal SF tested and correlated with the degree of radiographic degeneration (r = 0.55, p < 0.05). NTPPHase specific activity in ultracentrifugation pellets was highest in CPPD deposition disease fluids (p < 0.05). 127 kDa enzyme was found in both sedimentable and soluble fractions from CPPD, OA, TKA, and normal fluids, and was extensively degraded in all inflammatory fluids. Intact 115 kDa PC-1 was found only in the 2 CPPD fluids with the highest NTPPHase activity. 58 kDa enzyme was found in most fluids, predominantly in the soluble fraction. 127 kDa protein was identified in human synoviocyte conditioned media but not in cell lysate, while PC-1 and 58 kDa proteins were found in the cell lysate but not in the conditioned media.

CONCLUSION

There was no disease specific association with any one ecto-NTPPHase. Total enzyme activity correlated with the degree of degenerative change. The specific activity of pelletable 127 kDa enzyme was higher in fluids containing CPPD crystals. All 3 ecto-NTPPHases or their presumed degradation products were detectable in some pathologic and normal fluids. A 200 kDa reactive band often accompanied reactivity to the 127 kDa enzyme. PC-1 and 127 kDa proteins were extensively degraded in inflammatory SF, while 58 kDa protein was not. The relative contribution of each of these enzymes to inorganic pyrophosphate production by human joint tissues remains unclear.

Functional characterization of the ubiquitin variant encoded by the baculovirus Autographa californica

The marked evolutionary conservation of ubiquitin is assumed to arise from constraints imposed by folding, stability, and interaction of the polypeptide with various components of the ATP, ubiquitin-dependent degradative pathway. The present studies characterize the most divergent (75% identity) of the species-specific ubiquitin isoforms encoded as a late gene product of the baculovirus Autographa californica [Guarino, L. A. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 409-413]. Viral ubiquitin supports 40% of the rate of ATP-dependent degradation exhibited by eukaryotic ubiquitin. Inhibition of proteolysis correlated with a lower steady-state concentration of ubiquitin-conjugated degradative intermediates. Rate studies revealed that viral ubiquitin exerts its effect at the step of isopeptide ligase-catalyzed (E3) ubiquitin conjugation since viral and eukaryotic polypeptides are identical in their abilities to support ATP-coupled activation by E1 and transthiolation to E2 carrier proteins. Other studies demonstrated viral ubiquitin severely attenuated the rate of K48-linked multiubiquitin chain formation in E3-independent conjugation catalyzed by recombination yeast CDC34 or rabbit reticulocyte E232K but not chain elongation of alternate linkages formed by yeast RAD6 or human E2EPF. The latter observations suggest nonconserved positions on viral ubiquitin constitute recognition signals for K48-linked chain formation. Sequence comparison of species-specific ubiquitin isoforms indicates that nonconserved positions localized to a defined region on the polypeptide surface distinct from the basic face required for E1 binding. These results suggest this novel ubiquitin isoform may function in baculoviral replication to block destruction of a short-lived protein(s) by the host degradative pathway, targeted through either E2-catalyzed K48-linked multibiquitin chain formation or general E3-mediated conjugation.

Novel multiubiquitin chain linkages catalyzed by the conjugating enzymes E2EPF and RAD6 are recognized by 26 S proteasome subunit 5

Targeting of substrates for degradation by the ATP, ubiquitin-dependent pathway requires formation of multiubiquitin chains in which the 8.6-kDa polypeptide is linked by isopeptide bonds between carboxyl termini and Lys-48 residues of successive monomers. Binding of Lys-48-linked chains by subunit 5 of the 26 S proteasome regulatory complex commits the attached target protein to degradation with concomitant release of free ubiquitin monomers following disassembly of the chains. Point mutants of ubiquitin (Lys-->Arg) were used to map the linkage specificity for ubiquitin-conjugating enzymes previously demonstrated to form novel multiubiquitin chains not attached through Lys-48. Recombinant human E2EPF catalyzed multiubiquitin chain formation exclusively through Lys-11 of ubiquitin while recombinant yeast RAD6 formed chains linked only through Lys-6. Multiubiquitin chains linked through Lys-6, Lys-11, or Lys-48 each bound to subunit 5 of partially purified human 26 S proteasome with comparable affinities. Since chains bearing different linkages are expected to pack into distinct structures, competition between Lys-11 and Lys-48 chains for binding to subunit 5 demonstrates that the latter possesses determinants for recognizing alternatively linked chains and precludes the existence of subunit 5 isoforms recognizing distinct structures. In addition, competition studies provided an estimate of Kd < or = 18 nM for the intrinsic binding of Lys-48-linked chains of linkage number n > 4. This result suggests that the principal mechanistic advantage of multiubiquitin chain formation is to enhance the affinity of the associated substrate for the 26 S complex relative to that of unconjugated target protein. Complementation studies with E1/E2-depleted rabbit reticulocyte extract demonstrated RAD6 supported isopeptide ligase-dependent degradation only through Lys-48-linked chains, while E2EPF retained the ability to target a model radiolabeled substrate through Lys-11-linked chains. Therefore, the linkage specificity exhibited by these E2 isozymes depends on their catalytic context with respect to isopeptide ligase.

Characterization of a novel keratinocyte ubiquitin carrier protein

A novel member of the ubiquitin carrier protein family, designated E2EPF, has been cloned by our laboratory and expressed in a bacterial system in an active form. Ubiquitin carrier proteins, or E2s, catalyze one step in a multistep process that leads to the covalent conjugation of ubiquitin to substrate proteins. In this paper, we show that recombinant E2EPF catalyzes auto/multiubiquitination, the conjugation of multiple ubiquitin molecules to itself. Multiubiquitination has been shown previously to be required for targeting of a substrate protein for rapid degradation. Using a rabbit reticulocyte lysate system, E2EPF was shown to support the degradation of a model substrate in an ATP- and ubiquitin-dependent fashion. In contrast to a previous study which showed that selective protein degradation in one system is dependent upon multiubiquitination via the lysine 48 residue of ubiquitin, multiubiquitination, and proteolytic targeting by E2EPF was shown here to be independent of the lysine 48 multiubiquitin linkage. This functional characterization of E2EPF revealed a combination of features that distinguishes this enzyme from all previously characterized members of the ubiquitin carrier protein family. These results also suggest several possible autoregulatory models for E2EPF involving auto- and multiubiquitination.

Elevation of interferon beta-inducible proteins in ataxia telangiectasia cells

The recently cloned ATM gene has been shown to bear considerable homology to phosphatidylinositol 3 kinases and, therefore, its product may function in signal transduction. In this study, we report constitutively elevated levels of two IFN-beta-inducible proteins, ubiquitin cross-reactive protein (UCRP), and low molecular weight protein (LMP2), in human fibroblasts with the inherited disease ataxia telangiectasia (AT). Using immunoblotting, it was found that a M(r) 15,000 band representing free UCRP was hardly detectable in normal cells, while it was the predominant band in AT cells. Similarly, the expression of a M(r) 23,000 protein, LMP2 was found to be higher in AT cells than in normal cells. Culturing three successive passages of the AT cell line in the presence of different concentrations of neutralizing antibodies against IFN-beta caused partial and complete reduction, respectively, of the free UCRP and LMP2 signals to normal levels. These results indicate that UCRP and LMP2 pools may be basally elevated in AT cells due to constitutive activation of the IFN-beta induction pathway and are in keeping with the recently reported constitutive activation of the NF-kappaB transcriptional activator in AT cells.

Identification of a nucleotide pyrophosphohydrolase from articular tissues in human serum

OBJECTIVE

To characterize the nucleotide pyrophosphohydrolase (NTPPHase) in human serum.

METHODS

NTPPHase activity and kinetic analysis were performed using thymidine monophosphate paranitrophenyl ester (TMPNP) or 32Pgamma-labeled ATP as substrate. Sera were chromatographed (dye column), and peak fractions were analyzed kinetically and by immunoblot using antibodies to 127-kd articular cartilage vesicle (ACV) NTPPHase as well as to PC-1 and to 58 kd, two plasma membrane ecto-NTPPHases. Enzyme activity was measured before and after sample ultracentrifugation.

RESULTS

NTPPHase activity was found in all sera tested (2 normal subjects, 9 arthritis patients). Specific activity was increased 9-32-fold after chromatography; 60-80% of total activity was recovered in a single peak containing an approximately 100-kd soluble peptide related to the 127-kd ACV enzyme. The apparent Km of this peptide (TMPNP) was virtually identical to that of the porcine ACV 127-kd enzyme. No immunoreactivity against PC-1 or 58-kd NTPPHase was found.

CONCLUSION

Human serum NTPPHase is derived from 127-kd ACV-related enzyme.

Specificity of a porcine 127-kd nucleotide pyrophosphohydrolase for articular tissues

OBJECTIVE

To determine the tissue specificity of a porcine 127-kd nucleotide pyrophosphohydrolase (NTPPHase) found in vesicles derived from hyaline articular cartilage (ACV).

METHODS

Homogenates of porcine brain, lung, liver, kidney, urinary bladder, pancreas, spleen, skin, vena cava, marrow, bone (cells), tendon (Achilles), ligament (anterior cruciate), elastic cartilage, meniscus, and hyaline cartilage were analyzed for NTTPHase activity (thymidine monophosphate paranitrophenyl ester substrate) and by Western blot using polyclonal antibodies against 127-kd NTPPHase and against recombinant PC-1, another ecto-NTPPHase.

RESULTS

All tissues contained NTPPHase activity; the highest specific activity was found in hyaline articular cartilage, the lowest in brain. ACV-associated 127-kd NTTPHase was expressed in cartilage, ligament, and tendon. PC-1 was also expressed in those tissues and in skin, kidney, bone cells, and (probably) in liver and muscle.

CONCLUSION

The 127-kd NTPPHase appears to be highly specific for articular tissues.