Influence of granulocyte-macrophage colony-stimulating factor (GM-CSF) on whole blood endotoxin responsiveness following trauma, cardiopulmonary bypass, and severe sepsis

Major surgery, multiple injury, and severe sepsis lead to an impaired immune response. The suppressed status of the immune system is reflected by a reduced TNFalpha production of whole blood after stimulation with endotoxin in vitro and by a decreased HLA-DR expression on monocytes. In the present study, the effect of the immunostimulating hematopoetic growth factor GM-CSF on whole blood cultures of multiple injury, cardiac surgery, and severe sepsis patients was investigated. Endotoxin-induced TNFalpha production and HLA-DR expression was reduced in blood cultures of these patients compared to healthy donors. Preincubation with GM-CSF in vitro increased cytokine production in volunteers' and all patients' blood specimens in a dose-dependent manner. The elevation of cytokine response in cardiopulmonary bypass patients' blood, caused by in vitro preincubation with GM-CSF, equaled that of normal patients, whereas GM-CSF caused a lower rise of TNFalpha-producing capacity in blood of multiple-injury and sepsis patients. Further, GM-CSF treatment in vitro increased the down-regulated HLA-DR expression on monocytes prepared after cardiac surgery to a degree comparable to preoperative levels. Finally, GM-CSF incubation in vitro elevated TNFalpha synthesis in normal monocytes and in cells treated with a combination of the anti-inflammatory mediators IL-10, TGFbeta, and PGE2. These experiments show that hyporesponsiveness of whole blood induced by trauma, sepsis, or cardiac surgery is not irreversible but can be, at least in vitro, overridden by the immunostimulating compound GM-CSF.

Pak functions downstream of Dock to regulate photoreceptor axon guidance in Drosophila

The SH2/SH3 adaptor protein Dock has been proposed to transduce signals from guidance receptors to the actin cytoskeleton in Drosophila photoreceptor (R cell) growth cones. Here, we demonstrate that Drosophila p21-activated kinase (Pak) is required in a Dock pathway regulating R cell axon guidance and targeting. Dock and Pak colocalize to R cell axons and growth cones, physically interact, and their loss-of-function phenotypes are indistinguishable. Normal patterns of R cell connectivity require Pak's kinase activity and binding sites for both Dock and Cdc42/Rac. A membrane-tethered form of Pak (Pak(myr) acts as a dominant gain-of-function protein. Retinal expression of Pak(myr) rescues the R cell connectivity phenotype in dock mutants. These data establish Pak as a critical regulator of axon guidance and a downstream effector of Dock in vivo.

Structure of the small G protein Cdc42 bound to the GTPase-binding domain of ACK

The proteins Cdc42 and Rac are members of the Rho family of small GTPases (G proteins), which control signal-transduction pathways that lead to rearrangements of the cell cytoskeleton, cell differentiation and cell proliferation. They do so by binding to downstream effector proteins. Some of these, known as CRIB (for Cdc42/Rac interactive-binding) proteins, bind to both Cdc42 and Rac, such as the PAK1-3 serine/threonine kinases, whereas others are specific for Cdc42, such as the ACK tyrosine kinases and the Wiscott-Aldrich-syndrome proteins (WASPs). The effector loop of Cdc42 and Rac (comprising residues 30-40, also called switch I), is one of two regions which change conformation on exchange of GDP for GTP. This region is almost identical in Cdc42 and Racs, indicating that it does not determine the specificity of these G proteins. Here we report the solution structure of the complex of Cdc42 with the GTPase-binding domain ofACK. Both proteins undergo significant conformational changes on binding, to form a new type of G-protein/effector complex. The interaction extends the beta-sheet in Cdc42 by binding an extended strand from ACK, as seen in Ras/effector interactions, but it also involves other regions of the G protein that are important for determining the specificity of effector binding.

Dcdc42 acts in TGF-beta signaling during Drosophila morphogenesis: distinct roles for the Drac1/JNK and Dcdc42/TGF-beta cascades in cytoskeletal regulation

During Drosophila embryogenesis the two halves of the lateral epidermis migrate dorsally over a surface of flattened cells, the amnioserosa, and meet at the dorsal midline in order to form the continuous sheet of the larval epidermis. During this process of epithelial migration, known as dorsal closure, signaling from a Jun-amino-terminal-kinase cascade causes the production of the secreted transforming-growth-factor-beta-like ligand, Decapentaplegic. Binding of Decapentaplegic to the putative transforming-growth-factor-beta-like receptors Thickveins and Punt activates a transforming-growth-factor-beta-like pathway that is also required for dorsal closure. Mutations in genes involved in either the Jun-amino-terminal-kinase cascade or the transforming-growth-factor-beta-like signaling pathway can disrupt dorsal closure. Our findings show that although these pathways are linked they are not equivalent in function. Signaling by the Jun-amino-terminal-kinase cascade may be initiated by the small Ras-like GTPase Drac1 and acts to assemble the cytoskeleton and specify the identity of the first row of cells of the epidermis prior to the onset of dorsal closure. Signaling in the transforming-growth-factor-beta-like pathway is mediated by Dcdc42, and acts during the closure process to control the mechanics of the migration process, most likely via its putative effector kinase DPAK.

Manganese mineral interactions in brain

Manganese (Mn) is an essential mineral but is toxic when taken in excess. However, whether its interactions with other minerals in organs and cells are involved in mechanisms underlying Mn toxicity is poorly understood. We designed a developmental rat model of chronic Mn treatment (Group A: 1 mg MnCl2.4H2O per ml of drinking water; Group B: 10 mg MnCl2.4H2O per ml of drinking water; Group C: 20 mg MnCl2.4H2O per ml of drinking water; Control Group given water without manganese addition). Employing the model and instrumental neutron activation analysis, we investigated two hypotheses: (i) chronic manganese treatment alters the brain regional distribution of manganese and this altered manganese distribution also leads to region-specific changes of other metals; (ii) chronic manganese treatment induces differential changes in subcellular distributions of metals and electrolytes. In the treated rats, brain Mn level showed dose-related increases, the most pronounced being noted in striatum, hypothalamus, and hippocampus: these increases also led to alterations in regional distribution pattern of Mn. In the treated rats, Fe level was increased in hypothalamus, cerebellum, hippocampus, pons and medulla, and striatum. Cu level was increased in pons and medulla, hippocampus, midbrain, and striatum. Se level was increased in cerebellum, striatum, midbrain, hypothalamus, and pons and medulla. Zn level was increased in hypothalamus and striatum. Ca level was increased in midbrain but decreased in cerebellum; however, Mg and Al levels were not markedly affected. In brains of Mn-treated rats, Mn levels in subcellular fractions were all increased, being especially marked in nuclei, mitochondria, and synaptosomes; the subcellular distributions of Fe, Cu, Zn, and Mg were differentially altered although those of Al and Ca were minimally affected. These results are consistent with our hypotheses and may have implications in manganese neurotoxicity. The cellular and molecular mechanisms underlying manganese-mineral interactions in brain are still poorly defined and merit further investigation.

Randomized clinical trial of a new dexamethasone delivery system (Surodex) for treatment of post-cataract surgery inflammation

OBJECTIVE

To evaluate the safety of Surodex Drug Delivery System (Oculex Pharmaceuticals, Inc., Sunnyvale, CA) containing dexamethasone 60 micrograms, for use in cataract surgery, and to compare its anti-inflammatory efficacy with conventional dexamethasone 0.1% eyedrops.

DESIGN

Randomized, masked, and partially controlled trial.

PARTICIPANTS

Sixty eyes of 60 Asian patients undergoing extracapsular cataract extraction with intraocular lens implantation were examined. Of these, 28 eyes of 28 patients served as control eyes. Patients were stratified for age and presence of diabetes mellitus.

INTERVENTION

Surodex was inserted in the anterior chamber of 32 eyes at the conclusion of surgery. These eyes received placebo eyedrops four times a day after surgery for 4 weeks. Control eyes received neither Surodex nor a placebo implant but were prescribed conventional 0.1% dexamethasone eyedrops four times a day for 4 weeks.

MAIN OUTCOME MEASURES

Anterior chamber cells and flare were clinically graded at the slit lamp. Anterior chamber flare was objectively assessed with the Kowa FM500 Laser Flare Meter (Kowa Co. Ltd, Tokyo, Japan) for up to 3 months after surgery. Intraocular pressure and corneal endothelial specular microscopy with morphometric cell analysis were performed for up to 1 year after surgery.

RESULTS

Clinical slit-lamp assessment of anterior chamber flare and cells showed no difference between Surodex-treated eyes and dexamethasone eyedrop-treated eyes. Flare meter readings showed lower flare levels in the Surodex group at all postoperative visits compared with the dexamethasone eyedrop group. Flare reduction in the Surodex group reached statistical significance at days 4, 8, 15, and 30 after surgery. At 3 months, flare was reduced to preoperative levels in the Surodex group but was still raised in the dexamethasone eyedrop group. Five eyes in the dexamethasone eyedrop group required augmentation of steroids and were deemed therapeutic failures as opposed to one eye in the Surodex group. One patient in the dexamethasone eyedrop group developed postoperative open-angle glaucoma with profound visual field loss and optic disc cupping, resulting in hand movements vision. No significant difference in endothelial cell loss was noted between Surodex-inserted eyes and dexamethasone eyedrop-treated eyes for up to 1 year after surgery.

CONCLUSIONS

Intraocular placement of a single Surodex is a safe and effective treatment method to reduce intraocular inflammation after cataract surgery. There was no statistical difference in efficacy between Surodex and 0.1% dexamethasone eyedrops in reducing intraocular inflammation, as measured by clinical methods, while Surodex was clearly superior to eyedrops in reducing aqueous flare as objectively assessed with the laser flare meter.

Participation of small GTPases in dorsal closure of the Drosophila embryo: distinct roles for Rho subfamily proteins in epithelial morphogenesis

The Rho subfamily of Ras-related small GTPases participates in a variety of cellular events including organization of the actin cytoskeleton and signalling by c-Jun N-terminal kinase and p38 kinase cascades. These functions of the Rho subfamily are likely to be required in many developmental events. We have been studying the participation of the RHO subfamily in dorsal closure of the Drosophila embryo, a process involving morphogenesis of the epidermis. We have previously shown that Drac1, a Rho subfamily protein, is required for the presence of an actomyosin contractile apparatus believed to be driving the cell shape changes essential to dorsal closure. Expression of a dominant negative Drac1 transgene causes a loss of this contractile apparatus from the leading edge of the advancing epidermis and dorsal closure fails. We now show that two other Rho subfamily proteins, Dcdc42 and RhoA, as well as Ras1 are also required for dorsal closure. Dcdc42 appears to have conflicting roles during dorsal closure: establishment and/or maintenance of the leading edge cytoskeleton versus its down regulation. Down regulation of the leading edge cytoskeleton may be controlled by the serine/threonine kinase DPAK, a potential Drac1/Dcdc42 effector. RhoA is required for the integrity of the leading edge cytoskeleton specifically in cells flanking the segment borders. We have begun to characterize the interactions of the various small GTPases in regulating dorsal closure and find no evidence for the hierarchy of Rho subfamily activity described in some mammalian cell types. Rather, our results suggest that while all Ρ subfamily p21s tested are required for dorsal closure, they act largely in parallel.

Conjunctival rotation autograft for pterygium. An alternative to conjunctival autografting

OBJECTIVE

To determine the safety and efficacy of conjunctival rotation autografting (CRA) as an alternative to conventional conjunctival autograft after pterygium excision.

DESIGN

Prospective noncomparative case series.

PARTICIPANTS

Consecutive patients seen at the Pterygium Clinic of the Singapore National Eye Centre who were thought to be unsuitable for conventional conjunctival autografting underwent a modified surgical procedure, which the authors describe as CRA. There were 51 rotation autografts performed on 45 eyes of 43 patients.

INTERVENTION

In this procedure, the underlying fibrovascular pterygium tissue was removed and the original epithelium (with minimal subepithelial tissue included) replaced over the bare sclera with a 180 degrees rotation. Surgeries were performed by one surgeon (DT) from April 1995 to May 1996.

MAIN OUTCOME MEASURE

Pterygium recurrence and complications of CRA were measured.

RESULTS

The mean follow-up time was 12 months (range, 2-22 months). There were 46 primary and 5 recurrent pterygia. The indications for CRA were combined cataract and pterygium surgery (39.2%), double pterygia (31.4%), the need to preserve the superior conjunctiva (21.6%), and superior conjunctival scarring (7.8%). There were two recurrences (4% recurrence rate), one occurring at 4 months and the other occurring at 7 months after surgery. No significant complications were encountered. However, 50% of the grafts remained mildly injected for more than 3 months, and some remained injected for up to 13 months after surgery (average of 4 months). Pigmentary changes were also noted in six grafts (12%).

CONCLUSION

Conjunctival rotation autografting is a useful technique of conjunctival grafting in cases in which it is not possible or desirable to use the superior conjunctiva as a donor source.

Cellularization in Drosophila melanogaster is disrupted by the inhibition of rho activity and the activation of Cdc42 function

Regulation of cytoskeletal dynamics is essential for cell shape change and morphogenesis. Drosophila melanogaster embryos offer a well-defined system for observing alterations in the cytoskeleton during the process of cellularization, a specialized form of cytokinesis. During cellularization, the actomyosin cytoskeleton forms a hexagonal array and drives invagination of the plasma membrane between the nuclei located at the cortex of the syncytial blastoderm. Rho, Rac, and Cdc42 proteins are members of the Rho subfamily of Ras-related G proteins that are involved in the formation and maintenance of the actin cytoskeleton throughout phylogeny and in D. melanogaster. To investigate how Rho subfamily activity affects the cytoskeleton during cellularization stages, embryos were microinjected with C3 exoenzyme from Clostridium botulinum or with wild-type, constitutively active, or dominant negative versions of Rho, Rac, and Cdc42 proteins. C3 exoenzyme ADP-ribosylates and inactivates Rho with high specificity, whereas constitutively active dominant mutations remain in the activated GTP-bound state to activate downstream effectors. Dominant negative mutations likely inhibit endogenous small G protein activity by sequestering exchange factors. Of the 10 agents microinjected, C3 exoenzyme, constitutively active Cdc42, and dominant negative Rho have a specific and indistinguishable effect: the actomyosin cytoskeleton is disrupted, cellularization halts, and embryogenesis arrests. Time-lapse video records of DIC imaged embryos show that nuclei in injected regions move away from the cortex of the embryo, thereby phenocopying injections of cytochalasin or antimyosin. Rhodamine phalloidin staining reveals that the actin-based hexagonal array normally seen during cellularization is disrupted in a dose-dependent fashion. Additionally, DNA stain reveals that nuclei in the microinjected embryos aggregate in regions that correspond to actin disruption. These embryos halt in cellularization and do not proceed to gastrulation. We conclude that Rho activity and Cdc42 regulation are required for cytoskeletal function in actomyosin-driven furrow canal formation and nuclear positioning.

RhoA-binding kinase alpha translocation is facilitated by the collapse of the vimentin intermediate filament network

The regulation of morphological changes in eukaryotic cells is a complex process involving major components of the cytoskeleton including actin microfilaments, microtubules, and intermediate filaments (IFs). The putative effector of RhoA, RhoA-binding kinase alpha (ROKalpha), is a serine/threonine kinase that has been implicated in the reorganization of actin filaments and in myosin contractility. Here, we show that ROKalpha also directly affects the structural integrity of IFs. Overexpression of active ROKalpha, like that of RhoA, caused the collapse of filamentous vimentin, a type III IF. A RhoA-binding-deficient, kinase-inactive ROKalpha inhibited the collapse of vimentin IFs induced by RhoA in HeLa cells. In vitro, ROKalpha bound and phosphorylated vimentin at its head-rod domain, thereby inhibiting the assembly of vimentin. ROKalpha colocalized predominantly with the filamentous vimentin network, which remained intact in serum-starved cells. Treatment of cells with vinblastine, a microtubule-disrupting agent, also resulted in filamentous vimentin collapse and concomitant ROKalpha translocation to the cell periphery. ROKalpha translocation did not occur when the vimentin network remained intact in vinblastine-treated cells at 4 degreesC or in the presence of the dominant-negative RhoAN19 mutant. Transient translocation of ROKalpha was also observed in cells subjected to heat shock, which caused the disassembly of the vimentin network. Thus, the translocation of ROKalpha to the cell periphery upon overexpression of RhoAV14 or growth factor treatment is associated with disassembly of vimentin IFs. These results indicate that Rho effectors known to act on microfilaments may be involved in regulating the assembly of IFs. Vimentin when phosphorylated also exhibits reduced affinity for the inactive ROKalpha. The translocation of ROKalpha from IFs to the cell periphery upon action by activated RhoA and ROKalpha suggests that ROKalpha may initiate its own cascade of activation.

In situ hybridization with 33P-labeled RNA probes for determination of cellular expression patterns of liver transcription factors in mouse embryos

Murine hepatocyte nuclear factor-3beta (HNF-3beta) protein is a member of a large family of developmentally regulated transcription factors that share homology in the winged helix/fork head DNA binding domain and that participate in embryonic pattern formation. HNF-3beta also mediates cell-specific transcription of genes important for the function of hepatocytes, intestinal and bronchiolar epithelium, and pancreatic acinar cells. We have previously identified a hepatocyte and pancreatic cut-homeodomain transcription factor, HNF-6, which is required for HNF-3beta promoter activity. In this study, we used in situ hybridization studies of stage-specific embryos to demonstrate that HNF-6 and its target gene, HNF-3beta, are coexpressed in the foregut endoderm and in the pancreatic and hepatic diverticulum. More detailed analysis of HNF-6 and HNF-3beta's developmental expression patterns provides evidence of colocalization in hepatocytes, intestinal epithelium, and pancreatic ductal epithelium and exocrine acinar cells. In support of the role of HNF-6 in regulating HNF-3beta expression in developing hepatocytes, their liver expression levels are both transiently reduced between 14 and 15 days of gestation. At day 18 of gestation and in adult pancreas, HNF-6 and HNF-3beta transcripts remain colocalized in the exocrine acinar cells, but their expression patterns diverge in endocrine cells. HNF-3beta expression is restricted to the endocrine cells of the islets of Langerhans, whereas the ductal epithelium expresses HNF-6. We discuss these expression patterns with respect to specification of hepatocytes and differentiation of the endocrine and exocrine pancreas.

The crystal structure of the hyperthermophile chromosomal protein Sso7d bound to DNA

Sso7d and Sac7d are two small (approximately 7,000 Mr), but abundant, chromosomal proteins from the hyperthermophilic archaeabacteria Sulfolobus solfataricus and S. acidocaldarius respectively. These proteins have high thermal, acid and chemical stability. They bind DNA without marked sequence preference and increase the Tm of DNA by approximately 40 degrees C. Sso7d in complex with GTAATTAC and GCGT(iU)CGC + GCGAACGC was crystallized in different crystal lattices and the crystal structures were solved at high resolution. Sso7d binds in the minor groove of DNA and causes a single-step sharp kink in DNA (approximately 60 degrees) by the intercalation of the hydrophobic side chains of Val 26 and Met 29. The intercalation sites are different in the two complexes. Observations of this novel DNA binding mode in three independent crystal lattices indicate that it is not a function of crystal packing.

cAMP-induced morphological changes are counteracted by the activated RhoA small GTPase and the Rho kinase ROKalpha

Dramatic transient changes resulting in a stellate morphology are induced in many cell types on treatment with agents that enhance intracellular cAMP levels. Thrombin fully protects cells from this inductive effect of cAMP through the thrombin receptor. The protective effect of thrombin was shown to be Rho-dependent. Clostridium botulinum C3 exoenzyme, which inactivates RhoA functions, abolished the ability of thrombin to protect cells from responding to increased cAMP levels. A constitutively activated RhoAV14 mutant protein also prevented cells from responding to cAMP. RhoA can be specifically phosphorylated at Ser-188 by the cAMP-activated protein kinase A (PKA). We demonstrate that RhoAV14A188, which cannot be phosphorylated by PKA in vitro, is more effective than RhoAV14 in preventing cells from responding to cAMP and in inducing actin stress fiber formation. This suggests that PKA phosphorylation of RhoA impairs its biological activity in vivo. ROKalpha, a RhoA-associated serine/threonine kinase can also prevent cells from responding to cAMP with shape changes. Phosphorylation of RhoA by PKA in vitro decreases the binding of RhoA to ROKalpha. These results indicate that RhoA and cAMP have antagonistic roles in regulating cellular morphology and suggest that cAMP-mediated down-regulation of RhoA binding to its effector ROKalpha may be involved in this antagonism.

PAK promotes morphological changes by acting upstream of Rac

The serine/threonine kinase p21-activated kinase (PAK) has been implicated as a downstream effector of the small GTPases Rac and Cdc42. While these GTPases evidently induce a variety of morphological changes, the role(s) of PAK remains elusive. Here we report that overexpression of betaPAK in PC12 cells induces a Rac phenotype, including cell spreading/membrane ruffling, and increased lamellipodia formation at growth cones and shafts of nerve growth factor-induced neurites. These effects are still observed in cells expressing kinase-negative or Rac/Cdc42 binding-deficient PAK mutants, indicating that kinase- and p21-binding domains are not involved. Furthermore, lamellipodia formation in all cell lines, including those expressing Rac binding-deficient PAK, is inhibited significantly by dominant-negative RacN17. Equal inhibition is achieved by blocking PAK interaction with the guanine nucleotide exchange factor PIX using a specific N-terminal PAK fragment. We conclude that PAK, via its N-terminal non-catalytic domain, acts upstream of Rac mediating lamellipodia formation through interaction with PIX.

Cryptic Rac-binding and p21(Cdc42Hs/Rac)-activated kinase phosphorylation sites of NADPH oxidase component p67(phox)

Rac1 is a member of the Rho family of small molecular mass GTPases that act as molecular switches to control actin-based cell morphology as well as cell growth and differentiation. Rac1 and Rac2 are specifically required for superoxide formation by components of the NADPH oxidase. In binding assays, Rac1 interacts directly with p67(phox), but not with the other oxidase components: cytochrome b, p40(phox), or p47(phox) (Prigmore, E., Ahmed, S., Best, A., Kozma, R. , Manser, E., Segal, A. W., and Lim, L. (1995) J. Biol. Chem. 270, 10717-10722). Here, the Rac1/2 interaction with p67(phox) has been characterized further. Rac1 and Rac2 can bind to p67(phox) amino acid residues 170-199, and the N terminus (amino acids 1-192) of p67(phox) can be used as a specific inhibitor of Rac signaling. Deletion of p67(phox) C-terminal sequences (amino acids 193-526), the C-terminal SH3 domain (amino acids 470-526), or the polyproline-rich motif (amino acids 226-236) stimulates Rac1 binding by approximately 8-fold. p21(Cdc42Hs/Rac)-activated kinase (PAK) phosphorylates p67(phox) amino acid residues adjacent to the Rac1/2-binding site, and this phosphorylation is stimulated by deletion of the C-terminal SH3 domain or the polyproline-rich motif. These data suggest a role for cryptic Rac-binding and PAK phosphorylation sites of p67(phox) in control of the NADPH oxidase.

Development of tearing in preterm and term neonates

BACKGROUND

Although term and preterm infants have the capacity to secrete tears, the relative contribution of basal and reflex secretion of tears has not been previously assessed together in a prospective study. This information potentially has practical clinical importance.

OBJECTIVES

To measure basal and reflex tear secretion in preterm (30-37 weeks after conception) and term (38-42 weeks) newborns and to determine the developmental pattern of tear production.

METHODS

Tear secretion was evaluated by applying Schirmer tear test strips to the inferior fornix for 5 minutes before (reflex plus basal secretion) and after (basal secretion) applying a topical anesthetic agent.

RESULTS

Seventy infants (36 preterm and 34 term) were tested. Mean (+/- SD) basal tear secretion was 6.2 (+/- 4.5) mm in preterm and 9.2 (+/- 4.3) mm in term infants and increased progressively with increasing weight (P<.001) for all newborns. Mean (+/- SD) reflex tear secretion was 7.4 (+/- 4.8) mm in preterm and 13.2 (+/- 6.5) mm in term infants and also increased with increasing weight (P<.001) for all newborns.

CONCLUSIONS

Preterm infants have reduced reflex and basal tear secretion. This may mask the diagnosis of a nasolacrimal duct obstruction, concentrate topically applied medications, and allow corneas to quickly become dry during ophthalmological examination and treatment. By term, tear production in newborns is similar to that in adults.

Interaction between a cellular protein that binds to the C-terminal region of adenovirus E1A (CtBP) and a novel cellular protein is disrupted by E1A through a conserved PLDLS motif

Adenovirus E1A proteins immortalize primary animal cells and cooperate with several other oncogenes in oncogenic transformation. These activities are primarily determined by the N-terminal half (exon 1) of E1A. Although the C-terminal half (exon 2) is also essential for some of these activities, it is dispensable for cooperative transformation with the activated T24 ras oncogene. Exon 2 negatively modulates in vitro cooperative transformation with T24 ras as well as the tumorigenic and metastatic potentials of transformed cells. A short C-terminal sequence of E1A governs the oncogenesis-restraining activity of exon 2. This region of E1A binds with a cellular phosphoprotein, CtBP, through a 5-amino acid motif, PLDLS, conserved among the E1A proteins of human adenoviruses. To understand the mechanism by which interaction between E1A and CtBP results in tumorigenesis-restraining activity, we searched for cellular proteins that complex with CtBP. Here, we report the cloning and characterization of a 125-kDa protein, CtIP, that binds with CtBP through the PLDLS motif. E1A exon 2 peptides that contain the PLDLS motif disrupt the CtBP-CtIP complex. Our results suggest that the tumorigenesis-restraining activity of E1A exon 2 may be related to the disruption of the CtBP-CtIP complex through the PLDLS motif.

A conserved negative regulatory region in alphaPAK: inhibition of PAK kinases reveals their morphological roles downstream of Cdc42 and Rac1

AlphaPAK in a constitutively active form can exert morphological effects (E. Manser, H.-Y. Huang, T.-H. Loo, X.-Q. Chen, J.-M. Dong, T. Leung, and L. Lim, Mol. Cell. Biol. 17:1129-1143, 1997) resembling those of Cdc42G12V. PAK family kinases, conserved from yeasts to humans, are directly activated by Cdc42 or Rac1 through interaction with a conserved N-terminal motif (corresponding to residues 71 to 137 in alphaPAK). alphaPAK mutants with substitutions in this motif that resulted in severely reduced Cdc42 binding can be recruited normally to Cdc42G12V-driven focal complexes. Mutation of residues in the C-terminal portion of the motif (residues 101 to 137), though not affecting Cdc42 binding, produced a constitutively active kinase, suggesting this to be a negative regulatory region. Indeed, a 67-residue polypeptide encoding alphaPAK83-149 potently inhibited GTPgammaS-bound Cdc42-mediated kinase activation of both alphaPAK and betaPAK. Coexpression of this PAK inhibitor with Cdc42G12V prevented the formation of peripheral actin microspikes and associated loss of stress fibers normally induced by the p21. Coexpression of PAK inhibitor with Rac1G12V also prevented loss of stress fibers but not ruffling induced by the p21. Coexpression of alphaPAK83-149 completely blocked the phenotypic effects of hyperactive alphaPAKL107F in promoting dissolution of focal adhesions and actin stress fibers. These results, coupled with previous observations with constitutively active PAK, demonstrate that these kinases play an important role downstream of Cdc42 and Rac1 in cytoskeletal reorganization.

Amineptine and midazolam dependence

A case report of a patient with amineptine and midazolam dependence is presented. A literature search was done for other cases of amineptine abuse and their presentations and medical investigations are compared. This is the first locally reported case of amineptine abuse and highlights the fact that amineptine is a potential drug of abuse.

Myotonic dystrophy kinase-related Cdc42-binding kinase acts as a Cdc42 effector in promoting cytoskeletal reorganization

The Rho GTPases play distinctive roles in cytoskeletal reorganization associated with growth and differentiation. The Cdc42/Rac-binding p21-activated kinase (PAK) and Rho-binding kinase (ROK) act as morphological effectors for these GTPases. We have isolated two related novel brain kinases whose p21-binding domains resemble that of PAK whereas the kinase domains resemble that of myotonic dystrophy kinase-related ROK. These approximately 190-kDa myotonic dystrophy kinase-related Cdc42-binding kinases (MRCKs) preferentially phosphorylate nonmuscle myosin light chain at serine 19, which is known to be crucial for activating actin-myosin contractility. The p21-binding domain binds GTP-Cdc42 but not GDP-Cdc42. The multidomain structure includes a cysteine-rich motif resembling those of protein kinase C and n-chimaerin and a putative pleckstrin homology domain. MRCK alpha and Cdc42V12 colocalize, particularly at the cell periphery in transfected HeLa cells. Microinjection of plasmid encoding MRCK alpha resulted in actin and myosin reorganization. Expression of kinase-dead MRCK alpha blocked Cdc42V12-dependent formation of focal complexes and peripheral microspikes. This was not due to possible sequestration of the p21, as a kinase-dead MRCK alpha mutant defective in Cdc42 binding was an equally effective blocker. Coinjection of MRCK alpha plasmid with Cdc42 plasmid, at concentrations where Cdc42 plasmid by itself elicited no effect, led to the formation of the peripheral structures associated with a Cdc42-induced morphological phenotype. These Cdc42-type effects were not promoted upon coinjection with plasmids of kinase-dead or Cdc42-binding-deficient MRCK alpha mutants. These results suggest that MRCK alpha may act as a downstream effector of Cdc42 in cytoskeletal reorganization.

[Modification of immune response after polytrauma and cardiopulmonary bypass by hematopoietic growth factors]

Cardiac surgery and polytrauma result in an impaired immune response as it can be demonstrated by a reduced endotoxin-stimulated TNF alpha production of whole blood cultures ex vivo. The immune-stimulating hematopoetic growth factor GM-CSF is in vitro capable to antagonize the suppressed immune function after trauma and cardiac surgery and, therefore, GM-CSF represents a potential therapeutic for immune suppressed states.