Biomedical subjects

D K Miller

Publications and source records attributed to D K Miller.

At least 19 recordsLinked to original sources

PubMed1998

Characterization and quantitation of NF-kappaB nuclear translocation induced by interleukin-1 and tumor necrosis factor-alpha. Development and use of a high capacity fluorescence cytometric system.

A new quantitative cytometric technique, termed the ArrayScanTM, is described and used to measure NF-kappaB nuclear translocation induced by interleukin (IL)-1 and tumor necrosis factor-alpha (TNFalpha). The amount of p65 staining is measured in both the nuclei defined by Hoechst 33342 labeling and in the surrounding cytoplasmic area within a preselected number of cells/well in 96-well plates. Using this technique in synchronously activated human chondrocytes or HeLa cells, NF-kappaB was found to move to the nucleus with a half-time of 7-8 min for HeLa and 12-13 min for chondrocytes, a rate in each case about 4-5 min slower than that of Ikappa Balpha degradation. IL-1 receptor antagonist and anti-TypeI IL-1 receptor antiserum on the one hand and anti-TNFalpha and monoclonal anti-TNF receptor 1 antibodies on the other hand could be shown to respectively inhibit IL-1 and TNFalpha stimulation in both cell types. In contrast, a polyclonal anti-TNF receptor 1 antiserum exhibited both a 50% agonism and a 50% antagonism to a TNFalpha stimulation in a dose-dependent fashion, indicating that subtle functional responses to complex agonist and antagonist stimuli could be measured. The effects of different proteasome inhibitors to prevent Ikappa Balpha degradation and subsequent NF-kappaB translocation could also be discriminated; Leu-Leu-Leu aldehyde was only a partial inhibitor with an IC50 of 2 microM, while clastolactacystin beta-lactone was a complete inhibitor with an IC50 of 10 microM. The nonselective kinase inhibitor K252a completely inhibited both IL-1 and TNFalpha stimulation in both cell types with an IC50 of 0.4 microM. This concentration, determined after a 20-min stimulation, was shown to be comparable with that obtained for inhibition of IL-6 production induced by a 100-fold lower IL-1 and TNFalpha concentration measured after 17 h of stimulation. These results suggest that the ArrayScanTM technology provides a rapid, sensitive, quantitative technique for measuring early events in the signal transduction of NF-kappaB.

Biological Transport↗

PubMed1998

Effects of (-)-ephedrine on locomotion, feeding, and nucleus accumbens dopamine in rats.

The intent of the present study was to determine the effects of systemic injections of the sympathomimetic agent ephedrine (EPH) on extracellular dopamine (DA) levels within the rat nucleus accumbens (NAC) and to compare these effects with those of EPH on locomotion and on feeding. In experiment 1, adult male rats were prepared with an indwelling 3 mm microdialysis probe positioned within the NAC. The rats were injected (i.p.) with vehicle, 5, 10, or 20 mg/kg (-)-EPH with dialysates collected every 20 min for 100 min after drug injection. Systemic injections of 5, 10 or 20 mg/kg (-)-EPH significantly enhanced extracellular levels of NAC DA over baseline by 79%, 130%, and 400%. Systemic injection of 20 mg/kg EPH significantly reduced NAC levels of DOPAC and HVA by 37% and 31%. The effects of EPH on brain dopamine activity were stereospecific given that an additional group of rats injected with 20 mg/kg (+)-EPH exhibited smaller changes in NAC DA (< 25%), DOPAC (< 10%), and HVA levels (< 20%) than did rats injected with 20 mg/kg (-)-EPH. In experiment 2, adult male rats were injected (i.p.) with 0, 5, 10, or 20 mg/kg (-)-EPH prior to placement in automated activity chambers. Total distance traveled was significantly increased by 10 and 20 mg/kg (-)-EPH, but not by 5 mg/kg (-)-EPH. In experiment 3, adult male rats were injected (i.p.) with 0, 2.5, 5, or 10 mg/kg (-)-EPH or with 0, 2.5, 5, or 10 mg/kg (+)-EPH prior to a 30-min feeding test. Although each EPH enantiomer decreased feeding, (-)-EPH was more potent in feeding suppression than was (+)-EPH. The present results suggest that EPH may alter locomotion and feeding via an indirect action on brain dopamine activity.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1998

Prevalence and causes of undernutrition in medical outpatients.

PURPOSE: To assess the prevalence, common causes, and frequency of recognition and treatment of undernutrition in older and younger medical outpatients using a cross-sectional survey design with 2-year follow-up of undernourished subjects. PATIENTS AND METHODS: Charts of 1017 adult patients attending a hospital outpatient department were reviewed for the presence of undernutrition, and 85 patients meeting inclusion criteria for undernutrition were evaluated and followed for 2 years. An initial evaluation focused on nutritional, cognitive, and affective status and on nutritional attitudes using two subscales of the EAT-26 eating disorder inventory. After 2 years, initial data plus outpatient records were evaluated by 2 independent reviewers to determine a primary cause of undernutrition and to assess the recognition and treatment of undernutrition by the primary physician. RESULTS: Undernutrition was identified in 46 (11%) and 44 (7%) of older and younger subjects respectively; odds ratio (OR) (95% [confidence interval (CI)]) for older versus younger=1.65 (1.06 to 2.51). The primary cause of undernutrition differed between age groups but was deemed treatable in nearly 90% of all subjects. Undernutrition was recognized in 19 (43%) older subjects and 5 (12%) younger subjects (OR=5.47 [1.87 to 16.0]), and appropriate intervention(s) were instituted in 6 (14%) and 2 (5%) of older and younger subjects, respectively (OR=3.08 [0.668 to 14.21]). Older subjects scored higher on the EAT-26 oral control subscale than did younger subjects (4.7 versus 2.5, P=0.004) but similarly on the EAT-26 dieting subscale (5.2 versus 6.3, P=0.332); these relationships did not change with control for potentially confounding variables. CONCLUSIONS: In this study, undernutrition was relatively common, usually amenable to treatment, but frequently undetected and undertreated in both older and younger medical outpatients. Older undernourished subjects exhibited higher oral control needs than younger persons, which may have implications for the pathophysiology and treatment of their malnutrition. Further improvement in detection and intervention is warranted in both younger and older age groups.

Adult↗

PubMed1998

Predilection for frailty remedial strategies among black and white seniors.

BACKGROUND: Frailty prevention and remedial programs based on exercise, hormone replacement, and vitamin supplementation are becoming available for use with older patients, but success of these programs depends largely on seniors' willingness to participate. METHODS: We evaluated preferences for specific aspects of these programs using a sample of 359 older persons recruited from potential delivery sites. Main effects and subgroup analyses were done. RESULTS: Subjects preferred stretching, chair-based, walking, and dynamic balance exercises over lifting weights, dancing, hormone and vitamin therapy; exercising alone in their own homes over exercising in groups; and vitamins over hormones. Preferences were affected to some extent by sex, race, recruitment site, and functional status. However, subjects' willingness even to consider exercise was rarely as high as the desired levels of participation set forth in Healthy People 2000. CONCLUSIONS: Physicians and public health authorities need to educate older persons about effective methods to prevent or treat frailty.

Accidental Falls↗

PubMed1998

Decreasing hospitalization rates for older home care patients with symptoms of depression.

OBJECTIVE: To target medically ill older home care patients with symptoms of depression in order to reduce their rate of hospitalization. DESIGN: A case-control study. SETTING: A private, nonprofit home care organization, the Visiting Nurse Association of St. Louis. PARTICIPANTS: Home care patients 65 years of age and older with symptoms of depression who were participants of a Total Quality Management (TQM) intervention (n = 81) were compared with an historical control of home care patients 65 years of age and older with symptoms of depression (n = 69). INTERVENTION: Utilization of TQM principles to develop a plan including: (a) an educational seminar on depression for home care staff involved in the project; (b) letters to physicians introducing the TQM project; (c) use of the Geriatric Depression Scale (GDS) for screening; (d) recommendation to the primary physician of a home social service (SS) consultation for patients with a GDS of 10 to 14; (e) recommendation to the primary physician of three interventions for patients with a GDS > or = 15: home SS consultation + mental health (MH), or gerontological nurse (GN) consultation + antidepressant medication (a pharmacotherapeutic algorithm sent by facsimile to the primary physician upon request). OUTCOME MEASURES: Hospitalization rates of the control group compared with the TQM intervention group, the degree to which part (e) of the plan was implemented, and the effect this had on hospitalization rates. RESULTS: The TQM intervention patients had a higher mean age than the historical control patients but were not different in percent female, percent white race, percent with a caregiver in the home, functional status, and in 15 of 16 diagnostic categories. Overall, the TQM intervention group had a hospitalization rate of 23.5% (19/81) compared with a rate of 40.6% (28/69) for the historical control group (P = .024). For part (e) of the plan (56/81 patients had a GDS > or = 15), 29/56 (52%) received the recommended SS consultation, 50/56 (89%) received the recommended MH or GN consultation, and 32/56 (57%) received antidepressant medication. One type of intervention did not seem to lower hospitalization rates more than another although having received the MH or GN visits approached significance (12/50, 24%; P = .052) when compared with the control group. CONCLUSIONS: Utilization of TQM principles and the development of an intervention such as the one described here can decrease hospitalization rates for medically ill older home care patients with symptoms of depression.

Aged↗

PubMed1997

IL-1 beta-converting enzyme (ICE) is present and functional in human alveolar macrophages: macrophage IL-1 beta release limitation is ICE independent.

Tissue macrophages readily produce intracellular pro-IL-1beta in response to stimuli such as LPS, but are limited in mature IL-1beta release compared with blood monocytes. The mechanism of this IL-1beta control may provide important insights into the physiology of IL-1beta at the tissue level. Since it has been hypothesized that IL-1beta processing by the IL-1beta-converting enzyme (ICE) regulates IL-1beta release, we compared human alveolar macrophages and human blood monocytes for relative ICE expression and activation. Using immunoblots and enzyme-linked immunoassay for ICE, we demonstrate that alveolar macrophages do not differ from blood monocytes in antigenic p45 ICE. Furthermore, an indirect assay for functional ICE documents similar ICE activities in both monocytes and alveolar macrophages, i.e., similar concentrations of soluble synthetic ICE inhibitor (IC50 values of 0.3 +/- 0.01 and 0.6 +/- 0.2 microM, respectively) are required to block mature IL-1beta generation. However, as has been reported for THP-1 myelomonocytic cells, neither alveolar macrophages nor blood monocytes contain directly quantifiable levels of functional ICE forms (p22/p20 and p10) when assayed by immunoblots or by a sensitive capture ELISA that uses an irreversible, biotinylated ICE inhibitor. These findings document that the macrophage limitation in mature IL-1beta release is not due to a lack of ICE or to an inability to activate ICE. Finally, using a staged release assay, the time to half-maximum mature IL-1beta release is significantly depressed in macrophages compared with that in monocytes. Taken together, these findings suggest that macrophage IL-1beta export is regulated independently of ICE activation.

Adenosine Triphosphate↗

PubMed1997

Chronic cadmium exposure attenuates the conditioned reinforcing properties of morphine and fentanyl.

Adult male rats were exposed ad libitum for 40 days to 100 ppm cadmium chloride through their diet, or an identical diet with no added cadmium. Conditioned place preference (CPP) was conducted in a 2-chamber apparatus in which all drugs were paired with the least-preferred side as determined on a pre-test. In Experiment 1. control and cadmium-exposed rats received 0, 0.6, 1.25, 2.5, or 5 mg/kg morphine sulfate (i.p.) for 4 days, and vehicle only for 4 days. Control animals showed a preference for the drug-paired side at 1.25, 2.5, and 5 mg/kg while the cadmium-exposed rats showed a preference at 5 mg/kg only. In Experiment 2, rats were implanted with cannulae into the lateral ventricles and 0, 2, 5 micrograms morphine sulfate was administered intracerebroventricularly (i.c.v.). An attenuation by cadmium again was observed, as control animals showed a place preference at 2 and 5 micrograms and cadmium-exposed animals showed preference at 5 micrograms only. In Experiment 3, increasing doses of the mu-opioid receptor agonist fentanyl (0, 0.0004, 0.004, and 0.04 mg/kg) were systemically administered (s.c.) and rats tested for CPP. While cadmium animals showed place preference only at 0.04 mg/kg, control animals showed preference at 0.0004, 0.004, and 0.04 mg/kg. These findings are discussed within the framework of metal-induced disturbance of neurochemical function and/or associative processing, and the implications that such disturbances may have for drug seeking and taking.

Animals↗

PubMed1997

The interleukin-1 receptor-associated kinase is degraded by proteasomes following its phosphorylation.

Following interleukin (IL)-1 stimulation, the majority of the cellular interleukin-1 receptor-associated kinase (IRAK) translocates to a discrete subset of the Type I IL-1 receptor (IL-1R1) in MRC-5 human lung fibroblasts. As the IRAK becomes multiphosphorylated, it is degraded by proteasomes at a rate comparable to that of the degradation of the phosphorylated IkappaBalpha protein. Proteasome inhibitors block the degradation of phosphorylated IRAK and correspondingly increase the amount of IL-1R1 that can be coimmunoprecipitated with IRAK. The nonspecific kinase inhibitor K-252b blocks IRAK phosphorylation and degradation, but does not inhibit IRAK association with the IL-1R1 indicating that translocation of IRAK to the IL-1R1 and its phosphorylation are independent events. The IL-1 specificity of these effects is indicated by the lack of IRAK phosphorylation and degradation by IL-1 in the presence of the IL-1 receptor antagonist or by the activation of MRC-5 cells by tumor necrosis factor alpha. Long term exposure of MRC-5 cells to IL-1 desensitizes the resynthesized IkappaBalpha to IL-1, but not to tumor necrosis factor alpha stimulation, but no additional effects on IRAK are seen.

Biological Transport↗

PubMed1997

Brain and plasma levels of cocaine and benzoylecgonine in lead-expose and cadmium-exposed rats following acute or chronic intraperitoneal administration of cocaine.

Previous investigations of metal/cocaine interactions have shown that chronic oral exposure to inorganic lead or cadmium attenuates the psychoactive effects of acute or repeated administration of cocaine. The purpose of this investigation was to assess the possibility that such interactive effects may derive from metal-induced disturbances in cocaine pharmacokinetics, i.e., delivery of cocaine to critical biologic sites may be disrupted by metal contamination. In this study, adult male rats were exposed to purified diets containing 250 ppm lead acetate (Group Lead), 100 ppm cadmium chloride (Group Cadmium), or unadulterated laboratory chow (Group Control); n = 48/exposure condition. Following ad libitum access to their respective diets in the home cage for 45 days, half the animals from each exposure regimen received single daily IP injections of 5, 10, or 20 mg/kg cocaine HCl for a period of 7 days (n = 8/group). The remaining half the animals received repeated daily injections of saline during this pretreatment phase. On the day following pretreatment, animals previously receiving cocaine injections were administered a single cocaine test challenge at a dose equal to that received in pretreatment. Similarly, saline pretreatment animals received either 5, 10, or 20 mg/kg cocaine. The results of this investigation did not reveal reliable evidence of metal-related differences in brain levels of cocaine. Plasma cocaine and benzoylecgonine (BE) levels also were essentially the same for control and metal-exposed animals. The failure to show that lead or cadmium alters the disposition of cocaine in brain or plasma underscores the need to pursue alternative accounts of metal/cocaine interactions.

Animals↗

PubMed1997

Actin cleavage by CPP-32/apopain during the development of apoptosis.

Interleukin-1beta-converting enzyme (ICE)/ced-3 family proteases play key roles in apoptosis. However, cellular substrates for ICE family proteases involved in apoptosis are not well understood. We previously showed that actin is cleaved in vitro by an ICE family protease, distinct from ICE itself, which is activated during VP-16-induced apoptosis. In this report, we demonstrate that the actin-cleaving ICE-family protease in the apoptotic cell extract is the activated CPP-32/apopain. CPP-32 effectively cleaves actin protein to 15 kDa and 31 kDa fragments. Studies with an antibody raised against Gly-Gln-Val-Ile-Thr peptide, the N-terminal sequence of the cleaved 15 kDa actin fragment, showed that actin is also cleaved in vivo during the development of apoptosis. Moreover, Benzyloxycarbonyl-Glu-Val-Asp-CH2OC(O)-2,6,-dichlorobenzene (Z-EVD-CH2-DCB), a selective inhibitor of CPP-32(-like) protease, efficiently inhibited the cleavage of actin and the apoptosis of VP-16-treated U937 cells. Our present results indicate that actin is the substrate of CPP-32/apopain(-like) protease both in vitro and in vivo and suggest the role of actin in the control of cell growth and apoptosis.

Actins↗

PubMed1997

The interleukin-1 beta converting enzyme family of cysteine proteases.

Interleukin-1 beta converting enzyme (ICE) is the first enzyme of a new family of cysteine endoproteinases to be isolated and characterized. An overview of the structure and activity of ICE is outlined together with highlights of salient features common to members of each of the family members.

Amino Acid Sequence↗

PubMed1997

The role of the Caspase family of cysteine proteases in apoptosis.

Members of the ICE/Ced3 family are cysteine endoproteases that have been found to induce many of the proteolytic events observed during apoptosis. Because these proteases selectively recognize an Asp as the P1 residue at the cleavage site this newly emerging protease family has been called the Caspase family Cysteinyl aspartate-specific protease.

Amino Acid Sequence↗

PubMed1997

Chronic exposure to cadmium attenuates behavioral sensitization to morphine.

The purpose of this investigation was to assess the impact of dietary cadmium on morphine-induced changes in locomotor activity. Adult male rats were exposed ad libitum to an adulterated food supply containing 100 ppm added cadmium chloride, or an identical diet containing no added cadmium, for 45 days prior to testing for the locomotor activating effects of successive daily morphine administration (0, 5, 10, or 20 mg/kg per session) on locomotor activity. On day 1 of testing, increasing doses of morphine produced a dose-related suppression of activity, and this sedative effect was greater in control than in cadmium-exposed animals. Repeated morphine administration resulted in tolerance to the sedative effects of the drug, and a systematic elevation of locomotor activity over the 14-day testing period was observed, with the augmentation (sensitization) effect more pronounced in control than cadmium-exposed animals. There was no indication that conditioning (context) events played a role in the effects observed here.

Animals↗

PubMed1997

Body composition and age in African-American and Caucasian women: relationship to plasma leptin levels.

Leptin is a recently isolated peptide hormone released from adipocytes that has been postulated to play a role in appetite regulation and energy metabolism. Aging affects both food intake and body composition. Body composition is also affected by ethnicity. We have evaluated the relationships between serum leptin levels, age, body composition (by dual-energy x-ray absorptiometry), and hormonal parameters in a cross-sectional study of 94 women, 53 African-American (AAF) and 41 Caucasian (CF). Our hypotheses were as follows: (1) changes in body composition would be related to age in a sinusoidal pattern, (2) changes in serum leptin would parallel changes in body fat, (3) serum leptin levels would be influenced by body fat distribution, and (4) serum leptin would be related to serum concentrations of sex hormones. Serum leptin paralleled changes in body fat and body mass index (BMI) with age. In the entire group, serum leptin correlated closely with measures of body fat, including BMI and total fat mass, and there was no difference in leptin levels between the two ethnic groups. In simple regression analysis, serum leptin was related to both serum estradiol and testosterone. The relationship between serum leptin and trunk fat was linear in both groups, but significantly different in AAF and CF (P = .014). Serum leptin was associated with the trunk to lower-extremity fat ratio in CF (r = .67, P = .001) but not in AAF. Body fat was increased with advancing age until about 65 years and then declined. Measures of lean body mass declined linearly with age in the entire group, as well as both subgroups. In the entire group, total lean body mass and lean body mass corrected for BMI (lean body mass/BMI) were inversely related to age. In subjects aged less than 60 years AAF were stronger (P < .05) and had both a larger BMI and fat mass (P < .05) than CF. However, the patterns of age-related changes in fat body mass, lean body mass, and BMI were similar in both groups. In the entire group, multiple regression analysis indicated that the age, free thyroxine index (FTI), and leptin concentration were predictors of the body composition and distribution of trunk to lower-body fat. These observations indicate that there is a sinusoidal relationship between body fat and age, with a decline in body fat in extreme old age in both AAF and CF, and that serum leptin concentrations are more closely related to body fat and BMI than to age or ethnicity.

Absorptiometry, Photon↗

PubMed1996

Activation of an interleukin 1 converting enzyme-dependent apoptosis pathway by granzyme B.

Cytotoxic T lymphocytes (CTL) can induce apoptosis through a granzyme B-based killing mechanism. Here we show that in cells undergoing apoptosis by granzyme B, both p45 pro-interleukin 1 beta converting enzyme (ICE) and pro-CPP32 are processed. Using ICE deficient (ICE -/-) mice, embryonic fibroblasts exhibit high levels of resistance to apoptosis by granzyme B or granzyme 3, while B lymphoblasts are granzyme B-resistant, thus identifying an ICE-dependent apoptotic pathway that is activated by CTL granzymes. In contrast, an alternative ICE-independent pathway must also be activated as ICE -/- thymocytes remain susceptible to apoptosis by both granzymes. In ICE -/- B cells or HeLa cells transfected with mutant inactive ICE or Ich-1S that exhibit resistance to granzyme B, CPP32 is processed to p17 and poly(ADP-ribose) polymerase is cleaved indicating that this protease although activated was not associated with an apoptotic nuclear phenotype. Using the peptide inhibitor Ac-DEVD-CHO, apoptosis as well as p45 ICE hydrolysis are suppressed in HeLa cells, suggesting that a CPP32-like protease is upstream of ICE. In contrast, p34cdc2 kinase, which is required for granzyme B-induced apoptosis, remains inactive in ICE -/- B cells indicating it is downstream of ICE. We conclude that granzyme B activates an ICE-dependent cell death pathway in some cell types and requires a CPP32-like Ac-DEVD-CHO inhibitable protease acting upstream to initiate apoptosis.

Animals↗

PubMed1996

Sequential activation of three distinct ICE-like activities in Fas-ligated Jurkat cells.

ICE family proteases have been implicated as important effectors of the apoptotic pathway, perhaps acting hierarchically in a protease cascade. Using cleavage of endogenous protease substrates as probes, three distinct tiers of ICE-like activity were observed after Fas ligation in Jurkat cells. The earliest cleavage detected (30 min) was of fodrin, and produced a 150 kDa fragment. The second phase of cleavage (50 min) involved PARP, U1-70kDa and DNA-PKcs, all substrates of the CPP32-like proteases. Lamin B cleavage was observed during the third cleavage phase (90 min). Distinct inhibition profiles obtained using a panel of peptide-based inhibitors of ICE-like proteases clearly distinguished the three different cleavage phases. These studies provide evidence for a sequence of ICE-like proteolytic activity during apoptosis. The early fodrin cleavage, producing a 150 kDa fragment, identifies an ICE-like activity proximal to CPP32 in Fas-induced Jurkat cell apoptosis.

Antibodies, Monoclonal↗

PubMed1996

Activation of the native 45-kDa precursor form of interleukin-1-converting enzyme.

Active interleukin-1beta-converting enzyme (ICE) is composed of 20- and 10-kDa polypeptides (p20 and p10) derived from the processing of a cytosolic 45-kDa precursor protein (p45). The cleavage and activation of the native p45 ICE precursor have been characterized by use of specific inhibitors and antibodies recognizing various regions of ICE. The processing of p45 in vitro in THP.1 monocytic cell cytoplasmic extracts is inhibited only by protease inhibitors that inhibit ICE and not by inhibitors of other protease classes. The addition of L-742,395, a biotinylated irreversible ICE inhibitor, to these extracts labels only p45 and simultaneously inhibits p45 processing, demonstrating that the p45 has catalytic activity. Following a cleavage of p45 at a site that becomes the COOH terminus of p20, a more active intermediate is formed which migrates on SDS-polyacrylamide gel electrophoresis with an molecular mass of 35 kDa (ED50 of approximately 0.1 microM L-742,395 labeling versus 5 microM for p45). This new more active ICE form serves both as an intermediate enzyme to cleave p45 as well as a substrate for the formation of the final active ICE (ED50 of 1 nM L-742,395 labeling of p20 and for p22, an NH2-terminally extended form of p20). While initial cleavage of p45 can be found at the sites corresponding to both the NH2 termini of p22 and p20, these fragments cannot be labeled by L-742,395 and are hence inactive. p45 is not processed at the site corresponding to the NH2 terminus of the p10. Less than 50% of the p45 is cleaved down to active p20 or p22 ICE as determined by band shift on SDS-polyacrylamide gel electrophoresis of the biotinylated fragments, indicating that the in vitro activation is highly inefficient. The ICE fragmentation occurs by an intermolecular process and is highly dilution sensitive. Cleavage of p45 by exogenous p20/p10 ICE differs from that of the endogenous p45 cleavage activity in that the p20/p10 activity is more salt sensitive, and it produces a different pattern of cleavage fragments, principally 35- and 12-kDa fragments. These results indicate that the nature of the ICE activity changes as p45 is processed down to the p20/p10 form of the enzyme.

Amino Acid Sequence↗

PubMed1996

Apopain/CPP32 cleaves proteins that are essential for cellular repair: a fundamental principle of apoptotic death.

Proteolysis mediated by the interleukin 1 beta-converting enzyme (ICE) homologues is an important mechanism of the apoptotic process. The ICE homologue apopain/CPP-32/Yama (subsequently referred to as apopain) cleaves poly(ADP-ribose)polymerase (PARP) early during apoptosis. Additional apoptosis-specific protein cleavages have been observed in which the direct involvement of ICE-like proteases has been postulated. These substrates include the 70-kD protein component of the U1-ribonucleoprotein (U1-70kD), and the catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs). The present studies demonstrate that U1-70kD and DNA-PKcs are excellent substrates for apopain, with cleavage occurring at sites that are highly similar to the cleavage site within PARP. The fragments generated from isolated protein substrates by apopain are identical to those observed in intact apoptotic cells, in apoptotic cell extracts, and in normal cell extracts to which apopain has been added. Like PARP, cleavage of these substrates in apoptotic cell extracts is abolished by nanomolar concentrations of Ac-DEVD-CHO and micromolar amounts of Ac-YVAD-CHO, confirming the involvement of apopain or an apopain-like activity. We propose that a central function of apopain or similar homologues in apoptosis is the cleavage of nuclear repair proteins, thereby abolishing their critical homeostatic functions.

Amino Acid Sequence↗