Lambda-interacting protein, a novel protein that specifically interacts with the zinc finger domain of the atypical protein kinase C isotype lambda/iota and stimulates its kinase activity in vitro and in vivo

The members of the atypical subfamily of protein kinase C (PKC) show dramatic structural and functional differences from other PKC isotypes. Thus, in contrast to the classical or novel PKCs, they are not activated by diacylglycerol or phorbol esters. However, the atypical PKCs are the target of important lipid second messengers such as ceramide, phosphatidic acid, and 3'-phosphoinositides. The catalytic and pseudosubstrate sequences in the two atypical PKCs (lambda/iota PKC and zeta PKC) are identical but are significantly different from those of conventional or novel PKCs. It has been shown that microinjection of a peptide with the sequence of the pseudosubstrate of the atypical PKC isotypes but not of alpha PKC or epsilon PKC dramatically inhibited maturation and NF-kappa B activation in Xenopus oocytes, as well as reinitiation of DNA synthesis in quiescent mouse fibroblasts. This indicates that either or both atypical isoforms are important in cell signalling. Besides the pseudosubstrate, the major differences in the sequence between lambda/iota PKC and zeta PKC are located in the regulatory domain. Therefore, any functional divergence between the two types of atypical PKCs will presumably reside in that region. We report here the molecular characterization of lambda-interacting protein (LIP), a novel protein that specifically interacts with the zinc finger of lambda/iota PKC but not zeta PKC. We show in this paper that this interaction is detected not only in vitro but also in vivo, that LIP activates lambda/iota PKC but not zeta PKC in vitro and in vivo, and that this interaction is functionally relevant. Thus, expression of LIP leads to the transactivation of a kappa B-dependent promoter in a manner that is dependent on lambda/iota PKC. To our knowledge, this is the first report on the cloning and characterization of a protein activator of a PKC that binds to the zinc finger domain, which has so far been considered a site for binding of lipid modulators. The fact that LIP binds to lambda/iota PKC but not to the highly related zeta PKC isoform suggests that the specificity of the activation of the members of the different PKC subfamilies will most probably be accounted for by proteins like LIP rather than by lipid activators.

Evidence for a role of MEK and MAPK during signal transduction by protein kinase C zeta

Protein kinase C zeta (zeta PKC) is critically involved in the control of a number of cell functions, including proliferation and nuclear factor kappa B (NF-kappa B) activation. Previous studies indicate that zeta PKC is an important step downstream of Ras in the mitogenic cascade. The stimulation of Ras initiates a kinase cascade that culminates in the activation of MAP kinase (MAPK), which is required for cell growth. MAPK is activated by phosphorylation by another kinase named MAPK kinase (MEK), which is the substrate of a number of Ras-activated serine/threonine kinases such as c-Raf-1 and B-Raf. We show here that MAPK and MEK are activated in vivo by an active mutant of zeta PKC, and that a kinase-defective dominant negative mutant of zeta PKC dramatically impairs the activation of both MEK and MAPK by serum and tumour necrosis factor (TNF alpha). The stimulation of other kinases, such as stress-activated protein kinase (SAPK) or p70S6K, is shown here to be independent of zeta PKC. The importance of MEK/MAPK in the signalling mechanisms activated by zeta PKC was addressed by using the activation of a kappa B-dependent promoter as a biological read-out of zeta PKC.

Chlorpheniramine inhibits the synthesis of ornithine decarboxylase and the proliferation of human breast cancer cell lines

Proliferation of both mouse and human breast cancer cells was inhibited by chlorpheniramine (CPA) in a dose-response manner. At the beginning of the exponential phase of growth (two days after seeding), 250 microM CPA was able to reduce cell proliferation by 75% (in Ehrlich cell cultures) and 30% (in MCF-7 cultures). The antiproliferative effect of CPA was also tested on a poorly-differentiated and hormone-insensitive human breast cancer cell line (MDA-MB231) and on a highly proliferative human colon cancer cell line (clone 3). CPA was cytotoxic for MDA-MB231 cells at concentrations higher than 50 microM, and it was also cytotoxic for the colon cancer cell clone 3 at 250 microM CPA. Nevertheless, colon cancer cells were slightly stimulated at CPA concentrations less than 100 microM. CPA reduced (by 50-70%) the ornithine decarboxylase induction occurring early after culture seeding of experimental mammary tumors (Ehrlich carcinoma cells) and human breast cancer cells (MCF-7). The presented data suggest that in addition to ODC inhibition, CPA presents other still unknown cytotoxic effects.

Identification of heterogeneous ribonucleoprotein A1 as a novel substrate for protein kinase C zeta

The zeta isoform of protein kinase C (zeta PKC) has been shown to be an important step in mitogenic signal transduction. Using a yeast interaction screen to search for potential novel substrates of zeta PKC, we identified the heterogeneous ribonucleoprotein A1 (hnRNPA1). This protein specifically interacts with the catalytic domain of zeta PKC but not with its regulatory region or with the full-length protein, or with a kinase-defective mutant of the zeta PKC catalytic domain. In addition, no interaction was detected with other kinases such as Raf-1 or Mos, that, like zeta PKC, are critically involved in signal transduction, or with the catalytic domain of epsilon PKC, which is the PKC isotype with the highest homology to zeta PKC. hnRNPA1 is directly phosphorylated by both recombinant and native zeta PKC, and this phosphorylation is increased when zeta PKC is immunoprecipitated from mitogen-activated fibroblasts. As an additional control, hnRNPA1 is not phosphorylated appreciably by catalytic epsilon PKC or by a mixture of highly purified classical PKC isotypes maximally activated by phosphatidylserine and Ca2+. Treatment of quiescent cell cultures with a potent mitogen such as platelet-derived growth factor promotes a significant phosphorylation of hnRNPA1 in vivo that is impaired by expression of a dominant negative mutant of zeta PKC. Furthermore, expression of a catalytically active zeta PKC mutant phosphorylates hnRNPA1 in vivo. These findings suggest that zeta PKC could be critically involved in a novel pathway that connects membrane signaling to nuclear regulatory events, at the level of RNA transport and processing. Results also shown here by using different zeta PKC mutants suggesting the control of the cytoplasmic localization of hnRNPA1 by zeta PKC. Also of potential functional relevance are the results demonstrating that the phosphorylation by zeta PKC severely impairs both hnRNPA1 RNA binding and its ability to promote strand annealing in vitro.

Evidence for the in vitro and in vivo interaction of Ras with protein kinase C zeta

The zeta isoform of protein kinase C (zeta PKC) has been shown to be involved in the maturation of Xenopus oocytes and mitogenic signaling in fibroblasts. zeta PKC also regulates the important transcription factor nuclear factor kappa B, most probably by phosphorylation of the inhibitory molecule I kappa B. The mechanisms that control zeta PKC activity are still poorly characterized. This kinase is not activated by diacylglycerol but is potently stimulated in vitro by the products of phosphatidylinositol 3-kinase (PI 3-kinase), which suggests that zeta PKC is at least one of the critical targets of PI 3-kinase-triggered signals, and strengthens its role in cell proliferation. PI 3-kinase has been shown, like Raf, to be a direct effector of Ras. zeta PKC is a required step for Ras mitogenic signaling. Therefore, it is possible that zeta PKC directly interacts with Ras during mitogenic activation. We demonstrate here that Ras interacts in vitro with the regulatory domain of zeta PKC as well as that the association of zeta PKC with Ras in vivo is triggered by platelet-derived growth factor. It is also shown here that the expression of a dominant negative mutant of Ras (Asn-17) severely impairs the activation of zeta PKC in mouse fibroblasts.

Expression of different mitogen-regulated protein/proliferin mRNAs in Ehrlich carcinoma cells

Results from in vivo and from serum-free primary cultures of Ehrlich cells suggest that the expression of mitogen-regulated protein/proliferin (MRP/PLF) mRNAs is not essential for proliferation of this murine tumor. Two sizes for MRP/PRL-related open reading frames (ORFs) have been detected by reverse transcription/PCR amplification. They are almost identical to that reported for PLF-1; but 20% of the amplified cDNA included a shorter ORF, which lacks the entire sequence corresponding to that of the exon 3 of the mrp/plf genes. Ehrlich carcinoma may represent a good model to study regulation of expression and physiological roles of MRP/PLFs in vivo.

Protein kinase C zeta isoform is critical for kappa B-dependent promoter activation by sphingomyelinase

Recent evidence demonstrates that the protein kinase C zeta (zeta PKC) isoform is required for the activation of nuclear factor kappa B (NF-kappa B) and mitogenic signaling in Xenopus oocytes and mammalian cells. The mechanism whereby zeta PKC regulates NF-kappa B most probably involves the activation of a putative I kappa B kinase of molecular mass approximately 50 kDa, which phosphorylates and inactivates I kappa B. Tumor necrosis factor alpha (TNF alpha) and interleukin-1, besides activating the phospholipase C-mediated breakdown of phosphatidylcholine, also generate ceramide, which is produced by stimulation of sphingomyelin hydrolysis. We show here that exogenous addition of sphingomyelinase (SMase) to NIH-3T3 fibroblasts transactivates a kappa B-dependent chloramphenicol acetyltransferase reporter plasmid, to an extent similar to that produced by TNF alpha or phosphatidylcholine/phospholipase C. More importantly, the ability of SMase to stimulate this parameter is severely impaired by transfection of a zeta PKC kinase-defective dominant negative mutant, which suggests a critical role of zeta PKC in SMase signaling. In keeping with this notion, we also demonstrate here that zeta PKC is activated in vitro by ceramide and in vivo by treatment of NIH-3T3 fibroblasts with SMase.

zeta PKC induces phosphorylation and inactivation of I kappa B-alpha in vitro

The zeta isotype of protein kinase C (zeta PKC), a distinct PKC unable to bind phorbol esters, is required during NF-kappa B activation as well as in mitogenic signalling in Xenopus oocytes and mammalian cells. To investigate the mechanism(s) for control of cellular functions by zeta PKC, this enzyme was expressed in Escherichia coli as a fusion protein with maltose binding protein (MBP), to allow immobilization on amylose beads to study signalling proteins in cell extracts that might form complex(es) with zeta PKC. The following evidence for interaction with the NF-kappa B/I kappa B pathway was obtained. MBP-zeta PKC, but not MBP, bound and activated a potentially novel I kappa B kinase of approximately 50 kDa molecular weight able to regulate I kappa B-alpha function. Activation of the I kappa B kinase was dependent on zeta PKC enzymatic activity and ATP, suggesting that zeta PKC controls, directly or indirectly, the activity of a functionally significant I kappa B kinase. Importantly, zeta PKC immunoprecipitates from TNF-alpha-stimulated NIH-3T3 fibroblasts displayed a higher I kappa B phosphorylating activity than untreated controls, indicating the in vivo relevance of these findings. We also show here that zeta PKC associates with and activates MKK-MAPK in vitro, suggesting that one of the mechanisms whereby overexpression of zeta PKC leads to deregulation of cell growth may be accounted for at least in part by activation of the MKK-MAPK complex. However, neither MKK nor MAPK is responsible for the putative I kappa B phosphorylating activity. These data provide a decisive step towards understanding the functions of zeta PKC.

Zeta PKC plays a critical role during stromelysin promoter activation by platelet-derived growth factor through a novel palindromic element

Stromelysin is a metalloproteinase with the widest substrate specificity that plays a critical role in the induction of the metastatic phenotype in cancer cells. The mechanisms whereby growth factors and oncogenes control stromelysin expression are beginning to be characterized. We have recently demonstrated that protein kinase C isotypes down-regulatable by chronic exposure to phorbol esters are not involved in stromelysin gene expression in response to platelet-derived growth factor, ras oncogene, and phosphatidylcholine-hydrolyzing phospholipase C. We also identified a region in the stromelysin promoter, distinct from the 12-O-tetradecanoylphorbol-13-acetate-responsive element, responsible for the promoter activity in response to these stimulants. In this paper, we further characterize that promoter fragment and demonstrate that the region encompassing nucleotides -1218 to -1202, including the palindromic sequence ACTAGT, is necessary and sufficient for the control of stromelysin gene expression. The involvement of zeta-protein kinase C but not of c-raf in the stimulation of stromelysin promoter activity in response to platelet-derived growth factor is also demonstrated here. All these data suggest the existence of a bifurcation downstream of ras in the signaling mechanisms leading to stromelysin expression and DNA synthesis.

Protein kinase C zeta isoform is critical for mitogenic signal transduction

The requirement of protein kinase C zeta (zeta PKC) for maturation of X. laevis oocytes in response to insulin, p21ras, and phosphatidylcholine-hydrolyzing phospholipase C has recently been shown. Here we present experimental evidence demonstrating that activation of zeta PKC is not only necessary but also sufficient by itself to activate maturation in oocytes and to produce deregulation of growth control in mouse fibroblasts. Furthermore, by using a dominant kinase-defective mutant of zeta PKC, we confirm that this kinase is required for mitogenic activation in oocytes and fibroblasts. These results permit us to propose zeta PKC as a critical step downstream of p21ras in mitogenic signal transduction.

A dominant negative protein kinase C zeta subspecies blocks NF-kappa B activation

Nuclear factor kappa B (NF-kappa B) plays a critical role in the regulation of a number of genes. NF-kappa B is a heterodimer of 50- and 65-kDa subunits sequestered in the cytoplasm complexed to inhibitory protein I kappa B. Following stimulation of cells, I kappa B dissociates from NF-kappa B, allowing its translocation to the nucleus, where it carries out the transactivation function. The precise mechanism controlling NF-kappa B activation and the involvement of members of the protein kinase C (PKC) family of isotypes have previously been investigated. It was found that phorbol myristate acetate, (PMA) which is a potent stimulant of phorbol ester-sensitive PKC isotypes, activates NF-kappa B. However, the role of PMA-sensitive PKCs in vivo is not as apparent. It has recently been demonstrated in the model system of Xenopus laevis oocytes that the PMA-insensitive PKC isotype, zeta PKC, is a required step in the activation of NF-kappa B in response to ras p21. We demonstrate here that overexpression of zeta PKC is by itself sufficient to stimulate a permanent translocation of functionally active NF-kappa B into the nucleus of NIH 3T3 fibroblasts and that transfection of a kinase-defective dominant negative mutant of zeta PKC dramatically inhibits the kappa B-dependent transactivation of a chloramphenicol acetyltransferase reporter plasmid in NIH 3T3 fibroblasts. All these results support the notion that zeta PKC plays a decisive role in NF-kappa B regulation in mammalian cells.

Emotional distress in disaster victims. A follow-up study

One hundred thirteen adult victims of a major Latin American disaster were screened for emotional distress 1 and 5 years after the catastrophe. We used the Self-Reporting Questionnaire to identify emotionally distressed victims. Results indicate that the prevalence of emotional distress decreased from 65% in 1986 to 31% in 1990. However, a comparison of the symptomatology on these two assessments indicates a similarity in the frequency and profiles of symptoms among the distressed. Also, the most frequent symptoms and the strongest predictors of emotional distress were essentially the same. These findings provide empirical support to the clinically observed course of emotional symptomatology of disaster victims and to the focused training of health workers on selected emotional problems that are consistently present over time.

The use of glipizide combined with intensive insulin treatment for the induction of remissions in new onset adult type I diabetes

To determine if glipizide could enhance remission induction in new onset type 1 diabetes compared to intensive insulin treatment alone, 27 patients with type 1 diabetes were intensively treated in an open randomized trial with subcutaneous injections for one month. The insulin was randomly either discontinued (Group A) or the insulin discontinued and glipizide begun (Group B) Three patients in Group A (22%) and 7 in Group B (54%, p < .05) underwent insulin-free remissions for 10.3 +/- 4.4 and 8.7 +/- 2.6 months, respectively (p = NS). Mean blood glucose levels during insulin treatment were lower in patients entering remissions (94 +/- 3 mg/dl versus 102 +/- 5 mg/dl, p < 0.05). C-peptide levels were performed 0, 4, 8, and 24 weeks after insulin treatment. When all patients were examined, mean stimulated C-peptide levels at 4 weeks (0.58 +/- 0.09 pm/ml) were increased compared to time 0 (0.32 +/- 0.05 pm/ml, p < 0.02). Patients not entering remission had higher 4-week stimulated values (0.67 +/- 0.12 pm/ml) compared to time 0 values (0.29 +/- 0.06 pm/ml, p < .01), whereas remission patients' mean C-peptide levels remained similar at 0, 4, 8 and 24 weeks. These data indicate that a) insulin treatment plus glipizide induces higher rates of remission compared to intensive insulin treatment alone, b) the intensity of initial metabolic control may be an important determinant for remission induction, and c) endogenous insulin secretion is not associated with remission induction, suggesting that glipizide alters insulin sensitivity or is immunomodulatory in the context of new onset type 1 diabetes.

Putative prethymic T cell precursors within the early human embryonic liver: a molecular and functional analysis

Hematopoietic cells present in the liver in early human fetal life were characterized by phenotypic analysis using a broad panel of monoclonal antibodies. Expression of very late antigen 4 and leukocyte function-associated antigen 3 cell adhesion receptors and 4F2 cell activation molecules was found in all fetal liver hematopoietic cells before acquisition of T cell-, B cell-, or myeloid-specific surface markers, and before the time of intrathymic colonization. Molecular studies showed that expression of the interleukin 2 receptor beta (IL-2R beta) also occurred in the embryonic liver at this early ontogenic stage. In contrast, no expression of IL-2R alpha or IL-2 transcripts was found in fetal liver cells, whereas transcription of the IL-4 gene was detected in a small fetal liver cell subset. Putative T cell precursors were identified among the hematopoietic fetal liver cells by the expression of genes encoding the gamma, delta, epsilon, and zeta invariant chains of the CD3-T cell receptor (TCR) complex. However, no transcription of the polymorphic alpha and beta TCR genes was detected. Functional in vitro assays further demonstrated that fetal liver hematopoietic cells from those early embryos were capable of proliferating in response to T cell growth factors, including IL-4 and IL-2. However, whereas IL-4-induced proliferation paralleled the appearance in vitro of CD45+CD7-CD4dull cells expressing the CD14 myeloid antigen, as well as of CD34+ primitive hematopoietic progenitors, differentiation into CD45+CD7+CD8+CD3- immature T cells was observed when using IL-2. Moreover, coculture with thymic epithelial cell monolayers provided additional evidence that early fetal liver hematopoietic cells may include very primitive T cell precursors, which were able to differentiate in vitro into TCR alpha/beta+ mature T cells. Therefore, our results indicate that, after triggering of the T cell-specific maturation program in primitive fetal liver hematopoietic progenitors, specific signals provided intrathymically by epithelial cells may fulfill the requirements to drive terminal differentiation of prethymically committed T cell precursors.

Partial characterization of IR-alpha-MSH peptides found in melanoma tumors

Our previous work indicated that IR-alpha-MSH (immunoreactive alpha-melanocyte-stimulating hormone) plasma levels are three times as high in melanoma patients with progressing disease than in disease-free patients, and that the melanoma tumor itself may be the source of IR-alpha-MSH. Further identification of the material in tumor extracts has been carried out in this study, and the results presented here show that the immunoreactivity is associated with a major fraction of about 16 kDa and another of 5-9 kDa. Significant amounts of the immunoreactive material were also found in human melanoma cells but not in culture supernatants. The presence of this material may be related to the melanogenic status of the tumor cells. We have estimated the intracellular IR-alpha-MSH to be within a 0.4 to 2.3 nM range in melanoma tumor cells. We have investigated the melanogenic effect of the IR-alpha-MSH material and its relationship to alpha-MSH. Purified extracts both from metastases and cultured cells were found to promote frog skin darkening as well as tyrosinase activity in Cloudman S91 melanoma cells. The IR material could also displace labeled alpha-MSH from its binding sites in human melanoma cells. Our data clearly indicate that melanoma cells engage in an autocrine production of alpha-MSH-like bioactive peptides by melanoma cells, of larger mol.wt., which are able to bind to MSH receptors. These peptides may be involved in the regulation of melanogenesis and possibly in the growth and proliferation of melanoma cells by an autocrine/paracrine mechanism.

Human placental transfer of zinc: normal characteristics and role of ethanol

The fetal alcohol syndrome is primarily an impairment of growth and development. Zinc deficiency also causes abnormal fetal growth. Moreover, alcohol has been shown in some rodent studies to impair placental transport of zinc. The purpose of this investigation was to define better normal human placental zinc transport and the effects of alcohol on this process. To do this we employed the isolated perfused single cotyledon human term placental model, as well as the cultured human cytotrophoblast. In the perfused placental studies, it was shown that zinc is transferred by the placenta very slowly, about 6% of the rate of transport of antipyrine, a freely diffusible marker. The transfer is comparable in both directions, maternal to fetal and the reverse. Zinc does not cross the placenta against a zinc concentration gradient, in either direction. Rather there is good evidence of significant uptake (storage) of the zinc by the placenta on the recirculating compartment side of gradient studies. Moreover, when the perfusion fluid was low (0.2 g/100 ml) in albumin, about twice as much zinc accumulated in the perfused cotyledon and there was less zinc in the maternal compartment, as compared to perfusion with ten-fold higher (2.0 g/100 ml) albumin concentrations. Thus, ligand binding in the perfusate importantly influences placental zinc uptake. Interestingly, however, the increased placental binding of zinc did not translate into greater transfer of zinc to the fetal compartment. Thus, normal zinc transfer is slow, equal bidirectionally, and dependent on ligand binding in perfusate and placenta.(ABSTRACT TRUNCATED AT 250 WORDS)

Psychiatric disorders among poor victims following a major disaster: Armero, Colombia

We evaluated 102 adult victims of low socioeconomic status living in tent camps 8 months following the Armero disaster in Colombia to ascertain the level of psychiatric morbidity. Ninety-one percent of the subjects identified by the screening instrument as being emotionally distressed met DSM-III criteria for a psychiatric disorder. The most frequent diagnoses were posttraumatic stress disorder and major depression. These findings indicate that a simple screening instrument can be reliably used for the detection of significant emotional problems among disaster victims. They also show that these victims are not merely distressed; rather, they present clear and treatable psychiatric disorders that center on anxiety and depression. Interventions for their adequate management need to be designed, implemented, and evaluated. In a developing country, however, the high prevalence of mental disorders among disaster victims far exceeds the specialized mental health resources. The general health sector, particularly the primary level of care, must participate actively in the delivery of mental health services to meet this need, particularly for a socioeconomically disadvantaged population. The narrow range of psychiatric disorders detected among the disaster victims makes it possible to circumscribe the training of the primary care worker in disaster mental health to these priority conditions.

Alterations of ATP levels and of energy parameters in the blood of alcoholic and nonalcoholic patients with liver damage

Blood adenine nucleotides were determined in patients with alcoholic and non-alcoholic liver diseases. They included patients with alcoholic hepatitis (AH), alcoholic liver cirrhosis (ALC), non-alcoholic liver cirrhosis (NALC), and amoebic liver abscess (ALA) (28 patients). A decrease of 28% to 39% in blood ATP levels was observed among the patients with AH and the cirrhotic groups, respectively (p less than 0.05), whereas no significant changes in blood ATP levels were detected in the ALA group. Although total blood adenine nucleotides were significantly diminished in AH, ALC, and NALC groups, the AH patients retained their energy relationships within normal range. On the other hand, the cirrhotic groups, independently of their etiology, failed to maintain an adequate ATP/ADP ratio, energy charge, and phosphorylation potential in the blood, suggesting a decreased energy availability in their blood cells. Nevertheless, the mechanism involved in these effects remains to be elucidated, a failure of the damaged liver to supply purines to extra-hepatic tissues might be a major event altering the blood energy parameters.