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1.
AIDS Behav ; 27(4): 1140-1153, 2023 Apr.
Article in English | MEDLINE | ID: mdl-36367613

ABSTRACT

HIV/HCV prevention among people who inject drugs (PWID) is of key public health importance. We aimed to assess the impact of COVID-19 and associated response measures on HIV/HCV prevention services and socio-economic status of PWID in high-HIV-risk sites. Sites with recent (2011-2019) HIV outbreaks among PWID in Europe North America and Israel, that had been previously identified, were contacted early May 2020. Out of 17 sites invited to participate, 13 accepted. Semi-structured qualitative site reports were prepared covering data from March to May 2020, analyzed/coded and confirmed with a structured questionnaire, in which all sites explicitly responded to all 103 issues reported in the qualitative reports. Opioid maintenance treatment, needle/syringe programs and antiretroviral treatment /hepatitis C treatment continued, but with important reductions and operational changes. Increases in overdoses, widespread difficulties with food and hygiene needs, disruptions in drug supply, and increased homelessness were reported. Service programs rapidly reformed long established, and politically entrenched, restrictive service delivery policies. Future epidemic control measures should include mitigation of negative side-effects on service provision and socio-economic determinants in PWID.


RESUMEN: La prevención del VIH/VHC entre las personas que se inyectan drogas (PWID) es de vital importancia para la salud pública. Nuestro objetivo fue evaluar el impacto de COVID-19 y las medidas de respuesta asociadas en los servicios de prevención del VIH/VHC y el estado socioeconómico de las PWID en sitios de alto riesgo de VIH. Se contactó con sitios con brotes recientes (2011­2019) de VIH entre PWID en Europa, América del Norte e Israel, que habían sido previamente identificados, a principios de mayo de 2020. De los 17 sitios invitados a participar, 13 aceptaron. Se prepararon informes cualitativos semiestructurados del sitio que cubrían los datos de marzo a mayo de 2020, analizados/codificados y confirmados con un cuestionario estructurado, en el que todos los sitios respondieron explícitamente a los 103 asuntos reportados en los informes cualitativos. El tratamiento de mantenimiento con opiáceos, los programas de agujas/jeringas y el tratamiento antirretroviral/tratamiento de la hepatitis C continuaron, pero con importantes reducciones y cambios operativos. Se reportaron aumentos en las sobredosis, dificultades generalizadas con las necesidades alimentarias y de higiene, interrupciones en el suministro de medicamentos y aumento de personas sin hogar. Los programas de servicios reformaron rápidamente las políticas restrictivas de prestación de servicios, establecidas desde hace mucho tiempo y políticamente arraigadas. Las futuras medidas de control de epidemias deben incluir la mitigación de los efectos secundarios negativos en la prestación de servicios y los determinantes socioeconómicos en las PWID.


Subject(s)
COVID-19 , Drug Users , HIV Infections , Hepatitis C , Substance Abuse, Intravenous , Humans , Substance Abuse, Intravenous/complications , Substance Abuse, Intravenous/epidemiology , HIV Infections/epidemiology , HIV Infections/prevention & control , Pharmaceutical Preparations , Israel/epidemiology , Social Determinants of Health , COVID-19/epidemiology , COVID-19/prevention & control , Hepatitis C/epidemiology , Hepatitis C/prevention & control , Hepacivirus , Disease Outbreaks/prevention & control , Europe/epidemiology
2.
J Intellect Disabil Res ; 66(5): 483-498, 2022 05.
Article in English | MEDLINE | ID: mdl-35357054

ABSTRACT

BACKGROUND: Challenging behaviours in people with an intellectual developmental disorder (IDD) are complex and often difficult to understand. The developmental perspective may provide additional insights into the specific behavioural patterns and underlying motives in different emotional reference ages. METHODS: The behaviours of 185 adults with IDD who were admitted to psychiatry were systematically assessed with the Aberrant Behaviour Checklist (ABC) and the Modified Overt Aggression Scale (MOAS). The association of the different behaviours with various emotional reference age groups as assessed with the Scale of Emotional Development - Short (SED-S) was analysed to deduce behavioural patterns typical for a certain level of functioning. RESULTS: Overall, the severity of challenging behaviours decreases in higher emotional reference age groups. Physical aggression was most prevalent in persons in the second phase of emotional development (7-18 months reference age). In SED-S-1 (reference age 0-6 months), the persons appeared to be searching for physical comfort and showed high scores in social withdrawal, stereotypies and aggression towards the self. Persons functioning in SED-S-2 (reference age 7-18 months) scored highest in irritability and physical aggression (searching for security), while those in SED-S-3 (19-36 months) exhibited the searching for autonomy type characterised by defiant and socially inappropriate behaviours. Persons with an emotional reference age of 4-7 years (SED-S-4) showed inappropriate speech, verbal self-regulation and depressive-like behavioural aspects (searching for identity). CONCLUSIONS: The behavioural phenomena exhibited in a certain emotional reference age may support the clinician to differentiate behavioural problems from psychopathological symptoms to yield the proper diagnosis.


Subject(s)
Intellectual Disability , Problem Behavior , Adult , Aggression/psychology , Child , Child, Preschool , Developmental Disabilities , Emotions , Humans , Infant , Infant, Newborn , Intellectual Disability/psychology , Problem Behavior/psychology
4.
Hernia ; 24(6): 1371-1378, 2020 12.
Article in English | MEDLINE | ID: mdl-32170456

ABSTRACT

PURPOSE: Laparoscopic inguinal hernia repair (IHR) may lead to early postoperative pain. Therefore, opioid and non-opioid analgesic agents are often administered in the post-anesthesia care unit (PACU). To reduce the postoperative cumulative need of analgesic medication, as well as to accelerate the physical recovery time, the transversus abdominis plane (TAP) block has recently been studied. The TAP block is a regional anesthesia technique. Even though there is evidence about the efficacy of the block used in procedure such as an open inguinal hernia repair, the evidence regarding its use for the TAPP (transabdominal preperitoneal) technique remains low. We aim to provide more sufficient evidence regarding this topic. METHODS: A monocentric retrospective observational study investigating the effect of the TAP block prior to primary IHR in TAPP technique was conducted. The data of 838 patients who were operated on using this technique from June 2007 to February 2019 were observed. 72 patients were excluded because of insufficient information regarding their analgesic medication protocol. The patients' data were taken from their files. RESULTS: The patients in the TAP block group (n = 364) did not differ statistically significantly compared to the control group (n = 402) in terms of gender, BMI and age. Individuals of the TAP block group experienced less postoperative pain in the PACU (p < 0.001) and received less analgesic medication (morphine, oxycodone, piritramide, acetaminophen; p < 0.001). CONCLUSION: We assume that the TAP block is a sufficient approach to reduce postoperative pain and analgesic medication administration for IHR in TAPP technique.


Subject(s)
Abdominal Muscles/drug effects , Amidines/therapeutic use , Anesthesia, Local/methods , Hernia, Inguinal/drug therapy , Nerve Block/methods , Abdominal Muscles/surgery , Amidines/pharmacology , Female , Hernia, Inguinal/surgery , Humans , Male , Retrospective Studies
5.
Ecol Appl ; 29(6): e01951, 2019 09.
Article in English | MEDLINE | ID: mdl-31188494

ABSTRACT

Natural resource managers use data on the spatial range of species to guide management decisions. These data come from survey or monitoring efforts that use a wide variety of tools. Environmental DNA (eDNA) is a surveillance tool that uses genetic markers for detecting species and holds potential as a tool for large-scale monitoring programs. Two challenges of eDNA-based studies are uncertainties created by imperfect capture of eDNA in collection samples (e.g., water field samples) and imperfect detection of eDNA using molecular methods (e.g., quantitative PCR). Occurrence models can be used to address these challenges, thus we use an occurrence model to address two objectives: first, to determine how many samples were required to detect species using eDNA; second, to examine when and where to take samples. We collected water samples from three different habitat types in the Upper Mississippi River when both Bighead Carp and Silver Carp were known to be present based on telemetry detections. Each habitat type (backwater, tributary, and impoundment) was sampled during April, May, and November. Detections of eDNA for both species varied across sites and months, but were generally low, 0-19.3% of samples were positive for eDNA. Overall, we found that eDNA-based sampling holds promise to be a powerful monitoring tool for resource managers; however, limitations of eDNA-based sampling include different biological and ecological characteristics of target species such as seasonal habitat usage patterns as well as aspects of different physical environments that impact the implementation of these methods such as water temperature.


Subject(s)
Carps , Ecosystem , Animals , Ecology , Mississippi , Rivers
7.
Neth Heart J ; 25(1): 24-32, 2017 Jan.
Article in English | MEDLINE | ID: mdl-27752966

ABSTRACT

BACKGROUND: Without assistance, smokers being admitted to the hospital for coronary heart disease often return to regular smoking within a year. OBJECTIVE: This study assessed the 12-month effectiveness of a telephone and a face-to-face counselling intervention on smoking abstinence among cardiac patients. Differential effects for subgroups varying in their socioeconomic status and intention to quit smoking were also studied. METHODS: A randomised controlled trial was used. During hospital stay, smokers hospitalised for coronary heart disease were assigned to usual care (n = 245), telephone counselling (n = 223) or face-to-face counselling (n = 157). Eligible patients were allocated to an intervention counselling group and received nicotine patches. After 12 months, self-reported continued abstinence was assessed and biochemically verified in quitters. Effects on smoking abstinence were tested using multilevel logistic regression analyses applying the intention-to-treat approach. RESULTS: Compared with usual care, differential effects of telephone and face-to-face counselling on continued abstinence were found in patients with a low socioeconomic status and in patients with a low quit intention. For these patients, telephone counselling increased the likelihood of abstinence threefold (OR = 3.10, 95 % CI 1.32-7.31, p = 0.01), whereas face-to-face counselling increased this likelihood fivefold (OR = 5.30, 95 % CI 2.13-13.17, p < 0.001). Considering the total sample, the interventions did not result in stronger effects than usual care. CONCLUSION: Post-discharge telephone and face-to-face counselling interventions increased smoking abstinence rates at 12 months compared with usual care among cardiac patients of low socioeconomic status and low quit intentions. The present study indicates that patients of high socioeconomic status and high quit motivation require different cessation approaches.

8.
Leukemia ; 28(1): 59-69, 2014 Jan.
Article in English | MEDLINE | ID: mdl-23958923

ABSTRACT

Owing to their clinical success, there is growing interest in novel bispecific antibodies (bsAbs) for retargeting of T cells to tumor cells including for the treatment of acute myeloid leukemia (AML). One potential target for retargeting of T cells to AML blasts is the surface molecule CD33. Here we describe a novel modular targeting platform that consists of a universal effector module (EM) and individual target modules (TMs). Both modules can form an immune complex via a peptide epitope. The resulting targeting complex can functionally replace a conventional bsAb. By fusion of a costimulatory domain (for example, the extracellular CD137 ligand domain) to the TM, the targeting complex can even provide a costimulatory signal to the redirected T cells at their side of interaction with the tumor cell. Furthermore, we observed that an efficient killing of tumor cells expressing low levels of the tumor target CD33 becomes critical at low effector-to-target cell ratios but can be improved by costimulation via CD137 using our novel targeting system.


Subject(s)
Leukemia, Myeloid, Acute/immunology , Sialic Acid Binding Ig-like Lectin 3/immunology , T-Lymphocytes/immunology , Animals , Cell Line , Enzyme-Linked Immunosorbent Assay , Humans , Leukemia, Myeloid, Acute/pathology , Lymphocyte Activation , Male
9.
Cell Death Differ ; 17(11): 1795-804, 2010 Nov.
Article in English | MEDLINE | ID: mdl-20489726

ABSTRACT

Persistently hyperphosphorylated Akt contributes to human oncogenesis and resistance to therapy. Triciribine (TCN) phosphate (TCN-P), the active metabolite of the Akt phosphorylation inhibitor TCN, is in clinical trials, but the mechanism by which TCN-P inhibits Akt phosphorylation is unknown. Here we show that in vitro, TCN-P inhibits neither Akt activity nor the phosphorylation of Akt S473 and T308 by mammalian target of rapamycin or phosphoinositide-dependent kinase 1. However, in intact cells, TCN inhibits EGF-stimulated Akt recruitment to the plasma membrane and phosphorylation of Akt. Surface plasmon resonance shows that TCN, but not TCN, binds Akt-derived pleckstrin homology (PH) domain (K(D): 690 nM). Furthermore, nuclear magnetic resonance spectroscopy shows that TCN-P, but not TCN, binds to the PH domain in the vicinity of the PIP3-binding pocket. Finally, constitutively active Akt mutants, Akt1-T308D/S473D and myr-Akt1, but not the transforming mutant Akt1-E17K, are resistant to TCN and rescue from its inhibition of proliferation and induction of apoptosis. Thus, the results of our studies indicate that TCN-P binds to the PH domain of Akt and blocks its recruitment to the membrane, and that the subsequent inhibition of Akt phosphorylation contributes to TCN-P antiproliferative and proapoptotic activities, suggesting that this drug may be beneficial to patients whose tumors express persistently phosphorylated Akt.


Subject(s)
Acenaphthenes/metabolism , Acenaphthenes/pharmacology , Cell Membrane/metabolism , Proto-Oncogene Proteins c-akt/metabolism , Ribonucleotides/metabolism , Ribonucleotides/pharmacology , 3-Phosphoinositide-Dependent Protein Kinases , Animals , Apoptosis , Cell Line, Tumor , Epidermal Growth Factor/metabolism , Epidermal Growth Factor/pharmacology , Fluorescent Antibody Technique , Gene Amplification , Humans , Intracellular Signaling Peptides and Proteins/metabolism , Magnetic Resonance Spectroscopy , Membrane Proteins/metabolism , Phosphoproteins/chemistry , Phosphoproteins/metabolism , Phosphorylation/drug effects , Polymerase Chain Reaction , Protein Serine-Threonine Kinases/metabolism , Protein Structure, Tertiary , Proto-Oncogene Proteins c-akt/chemistry , Signal Transduction , Surface Plasmon Resonance , TOR Serine-Threonine Kinases/metabolism
10.
Oncogene ; 20(43): 6111-22, 2001 Sep 27.
Article in English | MEDLINE | ID: mdl-11593419

ABSTRACT

Protein phosphatase 1 (PP1) plays important roles in many different aspects of cellular activities including cell cycle control. One important function of PP1 is to activate the retinoblastoma protein pRB. Here we show that pRB is one of PP1's downstream targets during apoptosis. When HL-60 cells synchronized at the G1/S boundary were treated with pro-apoptotic cytosine arabinoside (araC), PP1alpha protein increased twofold and PP1 activity about 30% within 1 h. This was followed by pRB dephosphorylation, pRB cleavage by caspases, DNA fragmentation, the appearance of cells with <2n DNA content and finally, dying and dead cells. In vitro, pRB was protected from caspase-3 digestion by prior Cdk-mediated phosphorylation, whereas PP1alpha converted phospho-pRB into an efficient substrate for caspase-3. Introduction of active PP1alpha into HL-60 cells by electroporation was sufficient to induce characteristics of apoptosis. Similarly, araC-resistant cells, normally unable to die in response to araC, initiated apoptosis when electroporated with active PP1alpha. This was also accompanied by pRB cleavage. In contrast, introduction of inhibitor-2 delayed the onset of araC-induced apoptosis, whereas concomitant introduction of PP1alpha and inhibitor-2 completely prevented PP1alpha-induced apoptosis. These results suggest that dephosphorylation of key proteins by PP1alpha may be crucial for the initiation of apoptosis and further support the concept of PP1 serving as a potential target for anti-cancer therapy.


Subject(s)
Apoptosis/drug effects , Phosphoprotein Phosphatases/metabolism , Retinoblastoma Protein/metabolism , Antimetabolites, Antineoplastic/pharmacology , Blotting, Western , Caspase 3 , Caspases/metabolism , Cytarabine/pharmacology , DNA Fragmentation , Flow Cytometry , Genetic Vectors , HL-60 Cells , Humans , Phosphorylation , Precipitin Tests , Protein Binding , Protein Phosphatase 1 , Recombinant Proteins/metabolism , Substrate Specificity , Time Factors
11.
J Heart Valve Dis ; 9(6): 844-6, 2000 Nov.
Article in English | MEDLINE | ID: mdl-11128796

ABSTRACT

All mechanical heart valves are thrombogenic, and are associated with thromboembolic complications becomes ineffective. when anticoagulation Controversy exists with regard to the appropriate and safe anticoagulation regimen of gravid women with mechanical heart valve prostheses. While oral anticoagulants such as warfarin may be associated with fetal complications, the role of low-molecular weight heparin (LMWH) and heparinoids (and their respective appropriate dosage) have still to be determined. In developing countries such as Saudi Arabia, the prevalence of rheumatic fever is high, as is the percentage of female patients with mechanical heart valves and who are of child-bearing age. Thus, the issue of adequate anticoagulation on one hand, and avoidance of warfarin-induced embryopathy on the other hand, is crucial. To date, few reports are available of LMWH as sole anticoagulant in patients with mechanical heart valves. We report a case of massive valve thrombosis with subsequent pulmonary edema after warfarin anticoagulation was changed to LMWH during pregnancy, and administered at too low a dose.


Subject(s)
Anticoagulants/administration & dosage , Enoxaparin/administration & dosage , Heart Valve Prosthesis/adverse effects , Mitral Valve , Pregnancy Complications, Hematologic/prevention & control , Thrombosis/etiology , Adult , Dilatation and Curettage , Female , Heart Valve Prosthesis Implantation , Humans , Mitral Valve/surgery , Pregnancy , Pregnancy Complications, Cardiovascular , Pregnancy Complications, Hematologic/surgery , Preoperative Care , Thrombosis/prevention & control , Thrombosis/surgery , Treatment Failure
12.
J Biol Chem ; 274(41): 29470-5, 1999 Oct 08.
Article in English | MEDLINE | ID: mdl-10506210

ABSTRACT

We have shown earlier that, in cells expressing the retinoblastoma protein (pRB), a protein phosphatase (PP) 1alpha mutant (T320A) resistant to inhibitory phosphorylation by cyclin-dependent kinases (Cdks) causes G(1) arrest. In this study, we examined the cell cycle-dependent phosphorylation of PP1alpha in vivo using three different antibodies. PP1alpha was phosphorylated at Thr-320 during M-phase and again in late G(1)- through early S-phase. Inhibition of Cdk2 led to a small increase in PP1 activity and also prevented PP1alpha phosphorylation. In vitro, PP1alpha was a substrate for Cdk2 but not Cdk4. In pRB-deficient cells, phosphorylation of PP1alpha occurred in M-phase but not at G(1)/S. G(1)/S phosphorylation was at least partially restored after reintroduction of pRB into these cells. Consistent with this result, PP1alpha phosphorylated at Thr-320 co-precipitated with pRB during G(1)/S but was found in extracts immunodepleted of pRB in M-phase. In conjunction with earlier studies, these results indicate that PP1alpha may control pRB function throughout the cell cycle. In addition, our new results suggest that different subpopulations of PP1alpha regulate the G(1)/S and G(2)/M transitions and that PP1alpha complexed to pRB requires inhibitory phosphorylation by G(1)-specific Cdks in order to prevent untimely reactivation of pRB and permit transition from G(1)- to S-phase and/or complete S-phase.


Subject(s)
CDC2-CDC28 Kinases , Cell Cycle , Phosphoprotein Phosphatases/metabolism , Cyclin-Dependent Kinase 2 , Cyclin-Dependent Kinases/antagonists & inhibitors , Cyclin-Dependent Kinases/metabolism , Enzyme Inhibitors/pharmacology , G1 Phase , Humans , Immunoblotting , Kinetin , Phosphoprotein Phosphatases/antagonists & inhibitors , Phosphorylation , Phosphothreonine/metabolism , Protein Serine-Threonine Kinases/antagonists & inhibitors , Protein Serine-Threonine Kinases/metabolism , Purines/pharmacology , Recombinant Proteins/metabolism , Retinoblastoma Protein/metabolism , S Phase , Tumor Cells, Cultured
13.
Front Biosci ; 4: D22-42, 1999 Jan 01.
Article in English | MEDLINE | ID: mdl-9872729

ABSTRACT

Regulating the cell number is critically important for the development and maintenance of a multi-cellular organism. The cell number can be altered by inducing cell proliferation and/or programmed cell death (apoptosis). These two processes are linked by cell cycle-regulatory pathways, and protein phosphorylation and proteolytic degradation play key roles in both. Protein dephosphorylation has been a rather neglected aspect of cell cycle control. Recent advances in this field make it imperative to provide a view of the cell cycle from a phosphatase's vantage point. Although a number of protein phosphatases may be instrumental in cell cycle and apoptosis control, the emphasis here will be on the prototypical Ser/Thr-specific protein phosphatase PP1. Experiments will be considered in their historical context. The major goal of this review will be to re-evaluate the hypothesis that PP1 - and other protein phosphatases - may function as negative growth regulators. Currently available evidence suggests that PP1 activity is required for exit from mitosis, yet may also block cell cycle progression and facilitate apoptosis. Where appropriate, results highlighting the role of the other major phosphatase, PP2A, will also be discussed. This review will conclude with some unresolved issues including the question whether PP1 might be a suitable target for anti-cancer strategies.


Subject(s)
Cell Cycle/physiology , Phosphoprotein Phosphatases/physiology , Phosphorylation , Apoptosis , Cell Count , Cell Cycle Proteins/physiology , Cell Division , Cell Transformation, Neoplastic/pathology , Genes, Tumor Suppressor/physiology , Phosphoprotein Phosphatases/antagonists & inhibitors , Phosphoprotein Phosphatases/metabolism , Protein Processing, Post-Translational
16.
J Adolesc ; 20(4): 431-41, 1997 Aug.
Article in English | MEDLINE | ID: mdl-9268417

ABSTRACT

This study examines 144 older adolescents' perceptions of their parents' disclosure of their own lives to them. Information was obtained about the disclosure of 209 parents of college-aged children. The adolescents indicated whether and to what depth their parents had discussed 30 topics with them, and also indicated why they believed their parents had made these disclosures. The data indicate that college-age adolescents believe that their mothers disclose more to them than their fathers, especially about their problems. Mothers were also perceived to disclose for different, more emotional reasons than fathers, and they were perceived to seek advice more often.


Subject(s)
Attitude , Parent-Child Relations , Self Disclosure , Adolescent , Adult , Emotions , Female , Gender Identity , Humans , Male , Motivation , Problem Solving
17.
Hepatology ; 26(1): 176-85, 1997 Jul.
Article in English | MEDLINE | ID: mdl-9214467

ABSTRACT

To understand the regulation of receptor-mediated endocytosis in hepatocytes, we have used two specific inhibitors of serine-threonine protein phosphatases (PP), microcystin (MCYST) and okadaic acid (OKA) as probes to alter protein phosphorylation in hepatocytes. We have then examined the impact of these changes on the specific binding and uptake of transferrin (Tf) in hepatocytes. The measurement of PP activity in hepatocyte lysates showed that OKA and MCYST shared a common inhibition of protein phosphatase 2A (PP2A). Our results showed that both OKA (250 nmol/L) and MCYST (500 nmol/L) significantly reduced Tf uptake at steady state (P < or = .05). The measurement of Tf internalization after 15 minutes in protein phosphatase inhibitor-pretreated cells revealed that the initial uptake was also significantly reduced. Binding studies showed that pretreatment with either of the phosphatase inhibitors did not result in significant changes in the K(d) for Tf binding to transferrin receptor (TfR). Additionally, no significant changes in the number of TfR in the plasma membrane were observed in phosphatase inhibitor-pretreated cells. The treatment of hepatocytes with nocodazole (NOC), which results in microtubule disassembly and inhibition of microtubule-based vesicle transport, caused comparable reductions in initial and steady state levels of transferrin accumulation. The changes in transferrin accumulation by both phosphatase inhibitors and nocodazole were accompanied by redistribution of the microtubule-anchored Golgi apparatus and lysosomal network from the perinuclear region to the cell periphery. Our data show that the regulation of Tf uptake by receptor-mediated endocytosis is mediated by PP2A and additionally may occur through regulation of microtubule-based vesicle transport.


Subject(s)
Liver/metabolism , Phosphoprotein Phosphatases/metabolism , Receptors, Transferrin/metabolism , Animals , Antineoplastic Agents/pharmacology , Cells, Cultured , Enzyme Inhibitors/pharmacology , Fluorescent Antibody Technique, Indirect , Liver/drug effects , Male , Mice , Mice, Inbred C3H , Microcystins , Nocodazole/pharmacology , Okadaic Acid/pharmacology , Peptides, Cyclic/pharmacology , Protein Phosphatase 2 , Rats , Rats, Sprague-Dawley , Receptors, Transferrin/drug effects , Time Factors
18.
Curr Biol ; 7(6): 375-86, 1997 Jun 01.
Article in English | MEDLINE | ID: mdl-9197238

ABSTRACT

BACKGROUND: The retinoblastoma protein (Rb) needs to be phosphorylated by cyclin-dependent kinases (CDKs) before mammalian cells can enter the S phase of the cell cycle. As protein phosphatase 1 (PP1) activates Rb and is itself a target for inhibitory phosphorylation by CDKs in vitro, we asked whether any effects of PP1 on cell cycle progression depend on its phosphorylation and are mediated through Rb. RESULTS: Using electrotransfer of recombinant protein into Rb-positive and Rb-negative cells, we have compared the effects of a wild-type PP1 catalytic subunit, PP1alpha, and a constitutively active mutant of this subunit (PP1alphaT320A) on G1 progression, proliferation rates, and cell viability. In treated cells, PP1alpha levels were elevated 6-16-fold and remained stable for at least 48 hours. In Rb-positive cells, PP1alphaT320A, but not PP1alpha, caused cell cycle arrest in late G1, which was associated with a lack of Rb phosphorylation. In Rb-negative cells, neither wild-type nor mutant phosphatase caused any change in cell cycle progression. Increased cell death was observed in both Rb-positive and Rb-negative cells, however, upon introduction of excess PP1alpha. CONCLUSIONS: The difference between the effects of wild-type and mutant forms of PP1alpha suggests that PP1alpha has the potential to arrest cell growth in G1 unless it is inactivated by periodic phosphorylation at Thr320, presumably by CDKs that regulate passage through the G1-S cell cycle transition. Together, the effects in both cell types suggest that PP1alpha requires functional Rb to induce growth arrest, and that possibly another pool of PP1alpha induces cell death. This identifies PP1 as a potential target for therapeutic anti-proliferative strategies.


Subject(s)
Interphase/physiology , Phosphoprotein Phosphatases/metabolism , Retinoblastoma Protein/metabolism , Cell Death , Electroporation , Enzyme Activation , G1 Phase/physiology , HL-60 Cells , Humans , Mutation , Osteosarcoma , Phosphoprotein Phosphatases/genetics , Phosphorylation , Protein Conformation , Protein Phosphatase 1 , S Phase/physiology , Serum Albumin, Bovine/genetics , Serum Albumin, Bovine/metabolism , Time Factors , Tumor Cells, Cultured
19.
Am J Physiol ; 271(3 Pt 1): C929-43, 1996 Sep.
Article in English | MEDLINE | ID: mdl-8843724

ABSTRACT

To investigate the regulation of microtubule (MT)-based vesicle transport and the interphase MT array in hepatocytes, we have used okadaic acid (OKA) and microcystin (MCYST), two toxins that inhibit serine-threonine protein phosphatases (PP) 1 and 2A, to alter cellular phosphorylation. Video-enhanced differential interference contrast microscopy analysis revealed that both toxins inhibited the frequency, velocity, and run length of MT-dependent vesicle movements dose dependently between 50 and 500 nM. At our maximum dose of 500 nM, both toxins significantly decreased PP2A activity (OKA to 45 +/- 12% and MCYST to 57 +/- 2%), whereas PP1 was inhibited only by MCYST. Because no additional effects on vesicle movements were caused by MCYST over the changes caused by OKA, these data implicate PP2A in the regulation of MT-dependent vesicle movement. To understand whether the changes in parameters of vesicle movements were due to changes in the MT array, the effects of these toxins on MT distribution were examined by immunofluorescence microscopy. Although lower doses of OKA produced no effects, treatment with 500 nM OKA altered MT organization and also caused fragmentation and loss of acetylated (stable) MTs. In contrast, MCYST concentrations up to 500 nM elicited no changes in MT organization in general or in the acetylated (stable) array. From these findings we conclude that inhibition of MT-dependent vesicle movement by the PP inhibitors, MCYST and OKA, in hepatocytes cannot result from changes or disruption in the MT array. Because OKA (an inhibitor of PP2A only in our system) at high doses caused loss of stable MTs, whereas MCYST (an inhibitor of both PP1 and PP2A) did not, we conclude that the control of the preservation of the stable MT array in hepatocytes is complex. Stable MTs require active PP2A for maintenance, but the disruption of the array through inhibition of PP2A can be prevented if PP1 is also inhibited, suggesting that the relative degree of phosphorylation of multiple cellular components is the determinant of MT stability.


Subject(s)
Cytoplasmic Granules/drug effects , Liver/ultrastructure , Microtubules/drug effects , Phosphoprotein Phosphatases/pharmacology , Animals , Antineoplastic Agents/pharmacology , Biological Transport/drug effects , Liver/metabolism , Male , Nocodazole/pharmacology , Rats , Rats, Sprague-Dawley
20.
J Biol Chem ; 271(11): 5988-92, 1996 Mar 15.
Article in English | MEDLINE | ID: mdl-8626381

ABSTRACT

Several lines of evidence indicate that serine/threonine protein phosphatases may act as negative regulators of cellular growth. For example, treatment of cells with the tumor-promoter okadaic acid, an inhibitor of certain types of these phosphatases, resulted in the increased expression of several proto-oncogenes, indicating a negative role of the respective phosphatases in gene regulation. However, it was puzzling to find that okadaic acid-treated cells, even in the presence of highly expressed proto-oncogenes, did not proliferate, but were arrested at certain points of the cell cycle. To further analyze this discrepancy, we investigated the involvement of protein phosphatases in the control of other cell cycle regulatory genes, such as cdc2 which encodes an essential cell cycle regulatory kinase. We found that cdc2 gene expression was blocked by okadaic acid, but stimulated by protein phosphatase 2A. Protein phosphatase 2A is shown to be a positive regulator of cdc2 gene activity and to be required for cdc2 expression. Thus, our findings identify protein phosphatase 2A as a positive regulator of a major cell cycle regulatory gene and therefore suggest a stimulatory role of this enzyme in this aspect of cellular growth control.


Subject(s)
CDC2 Protein Kinase/genetics , Phosphoprotein Phosphatases/metabolism , 3T3 Cells , Animals , Base Sequence , Binding Sites/genetics , Cell Cycle/physiology , Cell Division/drug effects , Cell Division/genetics , Cell Division/physiology , DNA/genetics , DNA/metabolism , Enzyme Inhibitors/pharmacology , Ethers, Cyclic/pharmacology , Gene Expression Regulation, Enzymologic/drug effects , Genes, Regulator , Mice , Molecular Sequence Data , Okadaic Acid , Phosphoprotein Phosphatases/antagonists & inhibitors , Promoter Regions, Genetic , Protein Phosphatase 2 , Transfection
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