Analysing the impact of COVID-19 risk perceptions on route choice behaviour in train networks.

INTRODUCTION: Unlike previous pandemics, COVID-19 has sustained over a relatively longer period with cyclical infection waves and numerous variants. Public transport ridership has been hit particularly hard. To restore travellers' confidence it is critical to assess their risk determinants and trade-offs. METHODS: To this end, we survey train travellers in the Netherlands in order to: (i) quantify the impact of trip-specific, policy-based, and pandemic-related attributes on travellers' COVID-19 risk perceptions; and (ii) evaluate the trade-off between this risk perception and other travel attributes. Adopting the hierarchical information integration approach, in a two-stage stated preference experiment, respondents are asked to first rate how risky they perceive different travel situations to be, and then to choose between different travel options that include their own perceived risk rating as an attribute. Perceived risk ratings and choices between travel options are modelled using a linear regression and a mixed multinomial logit model, respectively. RESULTS: We find that on-board crowding and infection rates are the most important factors for risk perception. Amongst personal characteristics, the vulnerability of family and friends has the largest impact-nearly twice that of personal health risk. The bridging choice experiment reveals that while values of time have remained similar to pre-pandemic estimates, travellers are significantly more likely to choose routes with less COVID-19 risk (e.g., due to lower crowding). Respondents making longer trips by train value risk four times as much as their shorter trip counterparts. By combining the two models, we also report willingness to pay for mitigating factors: reduced crowding, mask mandates, and increased sanitization. CONCLUSION: Since we evaluate the impact of a large number of variables on route choice behaviour, we can use the estimated models to predict behaviour under detailed pandemic scenarios. Moreover, in addition to highlighting the importance of COVID-19 risk perceptions in public transport route choices, the results from this study provide valuable information regarding the mitigating impacts of various policies on perceived risk.

Interaction of myelin basic protein with the different components of the ATP,Mg-dependent protein phosphatase system.

Myelin basic protein (MBP) reduces the amount of phosphatase activity produced in the kinase FA-mediated activation of the ATP,Mg-dependent phosphatase. MBP was shown not only to inhibit the activated enzyme, but also to impair the kinase FA-mediated activation of the inactive phosphatase. In addition MBP prevents the time-dependent inactivation of the catalytic subunit by the modulator protein. These observations point to a regulatory role for MBP in the reversible activation of the ATP,Mg-dependent protein phosphatase by kinase FA.

Glycogen synthase kinase-3 and the Alzheimer-like state of microtubule-associated protein tau.

The Alzheimer-like state of tau protein includes phosphorylation by a proline-directed Ser/Thr kinase present in normal or pathological human brain. Extending earlier results on MAP kinase, we show here that the proline-directed kinase, GSK3, can induce an Alzheimer-like immune response involving several distinct and phosphorylatable epitopes at Ser-Pro motifs, as well as a gel mobility shift, similar to MAP kinase. Both kinases behave like microtubule-associated proteins in that they co-purify through cycles of assembly and disassembly, and both kinases are directly associated with paired helical filaments.

Neonatal neuronal overexpression of glycogen synthase kinase-3 beta reduces brain size in transgenic mice.

Glycogen synthase kinase-3beta (GSK-3beta) is important in neurogenesis. Here we demonstrate that the kinase influenced post-natal maturation and differentiation of neurons in vivo in transgenic mice that overexpress a constitutively active GSK-3beta[S9A]. Magnetic resonance imaging revealed a reduced volume of the entire brain, concordant with a nearly 20% reduction in wet brain weight. The reduced volume was most prominent for the cerebral cortex, without however, disturbing the normal cortical layering. The resulting compacted architecture was further demonstrated by an increased neuronal density, by reduced size of neuronal cell bodies and of the somatodendritic compartment of pyramidal neurons in the cortex. No evidence for apoptosis was obtained. The marked overall reduction in the level of the microtubule-associated protein 2 in brain and in spinal cord, did not affect the ultrastructure of the microtubular cytoskeleton in the proximal apical dendrites. The overall reduction in size of the entire CNS induced by constitutive active GSK-3beta caused only very subtle changes in the psychomotoric ability of adult and ageing GSK-3beta transgenic mice.

Inhibition of epidermal growth factor receptor tyrosine kinase activity by hypericin.

The naphthodianthrone hypericin produces a potent and irreversible inhibition of the epidermal growth factor (EGF) receptor tyrosine kinase activity. The inhibition was time and temperature dependent but did not depend on EGF activation. The IC50 values obtained were 0.37-8.7 microM with membranes incubated for 30 min at 30 degrees or 10 min at 0 degree, respectively. Kinetic analyses with poly(Glu,Ala,Tyr) 6:3:1 [poly(GAT)] as an exogenous substrate were in agreement with the irreversible nature of the inhibition. Irradiation for 30 min with fluorescent light caused a dramatic photosensitizing effect and resulted in an IC50 value of 44 nM. This effect was due to a type I mechanism, since the exclusion of oxygen did not alter the inhibition curve. The inhibition was inversely proportional to the amounts of membranes used, which probably reflects the non-specific sequestration of hypericin into the lipid bilayer. Ser/Thr protein kinases such as protein kinase A, casein kinase 1 and 2 and the enzyme 5'-nucleotidase, were not inhibited by hypericin not even at high concentrations (> 100 microM).

Early responses in mitogenic signaling, bombesin induced protein phosphorylations in Swiss 3T3 cells.

The amphibian tetradecapeptide bombesin as well as the bombesin-related mammalian peptides are potent mitogens for Swiss 3T3 cells. Other sole mitogens for Swiss 3T3 cells, such as PDGF and FGF, invariably signal through a tyrosine kinase receptor. The bombesin receptor has been cloned from Swiss 3T3 fibroblasts and was shown to be a member of the family of G-protein-linked neuropeptide receptors, whose sequence does not reveal a protein kinase domain. Upon binding to its receptor, bombesin evokes a complex cascade of early biochemical events including inositol 1,4,5-trisphosphate-induced mobilization of intracellular Ca2+, Na+ and K+ fluxes, PK-C activation, transmodulation of the EGF-receptor, accumulation and expression of the proto-oncogenes c-fos and c-myc and cAMP production. The intermediates in this signaling pathway are still largely unknown. Since many hormones and neuropeptides that signal through similar receptors with seven membrane spanning domains are by themselves not mitogenic for Swiss 3T3 fibroblasts, we suggest that bombesin acts through a rather special signaling pathway. Although its receptor does not feature a cytoplasmic tyrosine kinase domain, bombesin rapidly stimulates the tyrosine phosphorylation of multiple protein substrates, which are however quite distinct from the usual targets of tyrosine kinase receptors. Yet, a similar cascade of Ser/Thr protein kinases is activated downstream of these differentiating tyrosine kinase events, since, like EGF or insulin, bombesin rapidly stimulates the activity of two MBP kinases as well as several S6 peptide kinases. The present report furthermore implicates CK-2 in the early signal transduction pathway of this mitogen, and it is postulated that the activation of CK-2 may be an intrinsic property of "sole mitogens" like bombesin, as it may be a compulsory event leading to cell division. In that respect, CK-2 may also be the point of integration of multiple signaling pathways, initiated by several different growth factors which by their synergistic actions make cell proliferation possible.

Protein kinase D (PKD): a novel target for diacylglycerol and phorbol esters.

A novel serine/threonine protein kinase regulated by phorbol esters and diacylglycerol (named PKD) has been identified. PKD contains a cysteine-rich repeat sequence homologous to that seen in the regulatory domain of protein kinase C (PKC). A bacterially expressed NH2-terminal domain of PKD exhibited high affinity phorbol ester binding activity (Kd = 35 nM). Expression of PKD cDNA in COS cells conferred increased phorbol ester binding to intact cells. The catalytic domain of PKD contains all characteristic sequence motifs of serine protein kinases but shows only a low degree of sequence similarity to PKCs. The bacterially expressed catalytic domain of PKD efficiently phosphorylated the exogenous peptide substrate syntide-2 in serine but did not catalyse significant phosphorylation of a variety of other substrates utilised by PKCs and other major second messenger regulated kinases. PKD expressed in COS cells showed syntide-2 kinase activity that was stimulated by phorbol esters in the presence of phospholipids. We propose that PKD may be a novel component in the transduction of diacylglycerol and phorbol ester signals.

Pulse therapy with one-week itraconazole monthly for three or four months in the treatment of onychomycosis.

In an open study, twenty-eight patients with toenail onychomycosis were treated with monthly cycles of 400 mg itraconazole daily for one week for three (n = 5) or four (n = 23) consecutive months. In this patient sample, a total of seventy-one toenails were affected, with a mean nail-plate involvement of 55 percent (range, 20 to 100 percent). Trichophyton rubrum was the most frequently isolated pathogen, followed by T. mentagrophytes. After active therapy, patients were evaluated for a maximum period of two years (mean, twelve months). A total of twenty-six of twenty-eight patients (93 percent) were considered as clinically cured. Of the remaining two patients, one was markedly improved and one appeared to have relapsed. Only three of seventy-one nails still exhibited some pathologic involvement. Of the twenty-six patients considered cured, mycologic examination at the final visit was performed on thirteen and the results were negative in all of them. The remaining clinically cured patients had no mycologic examination at the last visit. This short treatment was well tolerated; the only adverse reaction being a mild headache in one patient. Patients preferred this regimen to receiving daily treatment for three months. Pulse therapy consisting of monthly one-week cycles of 400 mg itraconazole daily for three to four months may offer a new option for treatment of onychomycosis. Further large-scale studies are required to confirm these findings.

A novel splice variant of calcium and integrin-binding protein 1 mediates protein kinase D2-stimulated tumour growth by regulating angiogenesis.

Protein kinase D2 (PKD2) is a member of the PKD family of serine/threonine kinases, a subfamily of the CAMK super-family. PKDs have a critical role in cell motility, migration and invasion of cancer cells. Expression of PKD isoforms is deregulated in various tumours and PKDs, in particular PKD2, have been implicated in the regulation of tumour angiogenesis. In order to further elucidate the role of PKD2 in tumours, we investigated the signalling context of this kinase by performing an extensive substrate screen by in vitro expression cloning (IVEC). We identified a novel splice variant of calcium and integrin-binding protein 1, termed CIB1a, as a potential substrate of PKD2. CIB1 is a widely expressed protein that has been implicated in angiogenesis, cell migration and proliferation, all important hallmarks of cancer, and CIB1a was found to be highly expressed in various cancer cell lines. We identify Ser(118) as the major PKD2 phosphorylation site in CIB1a and show that PKD2 interacts with CIB1a via its alanine and proline-rich domain. Furthermore, we confirm that CIB1a is indeed a substrate of PKD2 also in intact cells using a phosphorylation-specific antibody against CIB1a-Ser(118). Functional analysis of PKD2-mediated CIB1a phosphorylation revealed that on phosphorylation, CIB1a mediates tumour cell invasion, tumour growth and angiogenesis by mediating PKD-induced vascular endothelial growth factor secretion by the tumour cells. Thus, CIB1a is a novel mediator of PKD2-driven carcinogenesis and a potentially interesting therapeutic target.

Immunohistochemical studies of protein kinase D (PKD) 2 expression in malignant human lymphomas.

AIM: To study the PKD2 expression, autophosphorylation and localization in reactive lymph nodes and tumors of lymphoid tissues. MATERIALS AND METHODS: Specific antibodies, which recognize PKD1/2 or PKD2 and autophosphorylated PKD1/2, were used for immunohistochemical and biochemical studies of tonsils, reactive lymph nodes, tumor samples of non-Hodgkin's lymphoma (NHL) and Hodgkin's lymphoma (HL). RESULTS: Immunohistochemical and biochemical analysis of PKD1 and PKD2 expression showed PKD2 expression in tonsils, reactive lymph nodes and tumor tissues from patients with NHL and HL. Furthermore, we were not able to reveal PKD1 expression in studied lymphoid tissues. In tonsils and reactive lymph nodes the PKD2 expression was detected in T and B cell zones with highest level in germinal centers of lymphoid follicles and the maximum level of autophosphorylation in the light zones of the germinal centers. We found that low level of PKD2 expression and autophosphorylation was characteristic feature for mantle cell lymphomas, Burkitt's lymphomas, and in 50% of CLL/small lymphocytic lymphomas. Lymphoma cells of germinal center origin and with activated B cell phenotype (diffuse large B cell lymphomas, HL) and anaplastic large cells lymphoma demonstrated the high level of PKD2 expression and autophosphorylation. CONCLUSIONS: The level of PKD2 expression and autophosphorylation in neoplastic cells corresponds to the expression pattern of this kinase in their normal analogs, and to the level of cell differentiation and activation.

Expression and characterization of PKD, a phorbol ester and diacylglycerol-stimulated serine protein kinase.

A novel protein kinase (named PKD) with an NH2-terminal region containing two cysteine-rich motifs has been expressed in COS-7 cells and identified as a receptor for phorbol esters. COS-7 cells transfected with a PKD cDNA construct (pcDNA3-PKD) exhibit a marked (4.8-fold) increase in [3H]phorbol 12,13-dibutyrate binding. An antiserum raised against the COOH-terminal 15 amino acids of PKD specifically recognized a single 110-kDa band in PKD-transfected cells. PKD prepared by elution from immunoprecipitates with the immunizing peptide efficiently phosphorylated the synthetic peptide syntide-2. The enzyme only poorly phosphorylated a variant syntide-2 where arginine 4 has been replaced by an alanine. The addition of [3H]phorbol 12,13-dibutyrate, 1-oleoyl-2-acetylglycerol, or 1,2-dioctanoyl-sn-glycerol in the presence of dioleoylphosphatidylserine stimulated the syntide-2 kinase activity of PKD in a synergistic fashion (4-6-fold). Furthermore, the autophosphorylation of PKD was strikingly stimulated by the same lipid activators (14-24-fold). Similar properties were found with PKD isolated from mouse lung. The substrate specificity of PKD is different from that of previously identified members of the protein kinase C family since it does not efficiently phosphorylate histone III-S, protamine sulfate, or a synthetic peptide based upon the conserved pseudosubstrate region of the protein kinase C family. Taken together, these data unambiguously establish PKD as a phorbol ester receptor and as a novel phospholipid/diacylglycerol-stimulated protein kinase.

Interleukin-8 activates microtubule-associated protein 2 kinase (ERK1) in human neutrophils.

The signal transduction initiated by the human cytokine interleukin-8 (IL-8), the main chemotactic cytokine for neutrophils, was investigated and found to encompass the stimulation of protein kinases. More specifically, IL-8 caused a transient, dose and time dependent activation of a Ser/Thr kinase activity towards myelin basic protein (MBP) and the MBP-derived peptide APRTPGGRR patterned after the specific concensus sequence in MBP for ERK enzymes. The activated MBP kinase was furthermore identified as an extracellular signal regulated kinase (ERK1) based on several criteria such as substrate specificity, molecular weight, activation-dependent mobility shift, and recognition by anti-ERK antibodies. For comparison, the chemotactic response of neutrophils to a stimulus of bacterial origin (fMet-Leu-Phe or fMLP) was also examined and found to involve the activation of a similar ERK enzyme. The present data clearly indicate that in terminally differentiated, non-proliferating human cells, the MBP kinase/ERK activity can serve other purposes than mitogenic signaling, and that processes such as chemotaxis, induced by bacterial peptides as well as by human cytokines like IL-8, involve the regulation of ERK enzymes.

Molecular cloning and characterization of protein kinase D: a target for diacylglycerol and phorbol esters with a distinctive catalytic domain.

A serine/threonine protein kinase that binds phorbol esters and diacylglycerol (named protein kinase D, PKD) has been identified. PKD contains membrane localization signals and a cysteine-rich repeat sequence homologous to that seen in the regulatory domain of protein kinase C (PKC). A bacterially expressed N-terminal domain of PKD exhibited high-affinity phorbol ester binding activity (Kd = 35 nM). The diacylglycerol analog 1-oleoyl-2-acetylglycerol inhibited phorbol ester binding in a dose-dependent manner. The catalytic domain of PKD contains all characteristic sequence motifs of serine protein kinases but shows only a low degree of sequence similarity to PKCs. The highest identity is with the catalytic domain of myosin light-chain kinase from Dictyostelium (41%). The bacterially expressed catalytic domain of PKD efficiently phosphorylated the exogenous peptide substrate syntide 2 in serine but did not catalyze significant phosphorylation of a variety of other substrates used by PKCs and other major second messenger regulated kinases. PKD may be an unusual component in the transduction of diacylglycerol and phorbol ester signals.

Transforming growth factor alpha activates Ha-Ras in human pancreatic cancer cells with Ki-ras mutations.

BACKGROUND & AIMS: The aim of this study was to identify signaling pathways that mediate cell proliferation in response to a Ras-activating growth factor, transforming growth factor (TGF)-alpha, in two pancreatic cancer cell lines with constitutively active Ki-Ras, MiaPaCa-2, and Panc-1. METHODS: ERK1/-2- and p90(rsk) activation were determined by immune complex kinase assays. AP-1 and E74 activation were assessed in transient transfections using luciferase reporter plasmids. Ha-Ras activation was determined using a glutathione S-transferase fusion protein comprising the Ras-binding domain of Raf and by immunocytochemistry, growth by DNA synthesis and colony formation in softagar. RESULTS: TGF-alpha stimulated activation of ERK1/-2, which was dependent on MEK-1, but independent of PKC activity. TGF-alpha-induced activation of an AP-1 reporter plasmid also required MEK-1 and Ras activity. Using an E74 reporter plasmid, we demonstrate that TGF-alpha indeed activates Ras in both cell lines. In particular, TGF-alpha induced membrane translocation and activation of the Ras isoform Ha-Ras. Finally, TGF-alpha-stimulated DNA synthesis and clonal growth in soft agar were prevented by treatment of cells with a MEK-1 inhibitor or a Ras farnesyl transferase inhibitor. CONCLUSIONS: The Ha-Ras-ERK cascade plays an important role in TGF-alpha-induced growth of pancreatic cancer cells with activating Ki-ras mutations. Inhibitors of this cascade could constitute novel anticancer agents for pancreatic tumors.

Protein kinase D (PKD) activation in intact cells through a protein kinase C-dependent signal transduction pathway.

Protein kinase D (PKD) is a serine/threonine protein kinase that is directly stimulated in vitro by phorbol esters and diacylglycerol in the presence of phospholipids. Here, we examine the regulation of PKD in living cells. Our results demonstrate that tumour-promoting phorbol esters, membrane-permeant diacylglycerol and serum growth factors rapidly induced PKD activation in immortalized cell lines (e.g. Swiss 3T3 and Rat-1 cells), in secondary cultures of mouse embryo fibroblasts and in COS-7 cells transiently transfected with a PKD expression construct. PKD activation was maintained during cell disruption and immunopurification and was associated with an electrophoretic mobility shift and enhanced 32P incorporation into the enzyme, but was reversed by treatment with alkaline phosphatase. PKD was activated, deactivated and reactivated in response to consecutive cycles of addition and removal of PDB. PKD activation was completely abrogated by exposure of the cells to the protein kinase C inhibitors GF I and Ro 31-8220. In contrast, these compounds did not inhibit PKD activity when added directly in vitro. Co-transfection of PKD with constitutively activated mutants of PKCs showed that PKCepsilon and eta but not PKCzeta strongly induced PKD activation in COS-7 cells. Thus, our results indicate that PKD is activated in living cells through a PKC-dependent signal transduction pathway.

Protein kinase D regulates the fission of cell surface destined transport carriers from the trans-Golgi network.

When a kinase inactive form of Protein Kinase D (PKD-K618N) was expressed in HeLa cells, it localized to the trans-Golgi network (TGN) and caused extensive tubulation. Cargo that was destined for the plasma membrane was found in PKD-K618N-containing tubes but the tubes did not detach from the TGN. As a result, the transfer of cargo from TGN to the plasma membrane was inhibited. We have also demonstrated the formation and subsequent detachment of cargo-containing tubes from the TGN in cells stably expressing low levels of PKD-K618N. Our results suggest that PKD regulates the fission from the TGN of transport carriers that are en route to the cell surface.

Recruitment of protein kinase D to the trans-Golgi network via the first cysteine-rich domain.

Protein kinase D (PKD) is a cytosolic protein, which upon binding to the trans-Golgi network (TGN) regulates the fission of transport carriers specifically destined to the cell surface. We have found that the first cysteine-rich domain (C1a), but not the second cysteine-rich domain (C1b), is sufficient for the binding of PKD to the TGN. Proline 155 in C1a is necessary for the recruitment of intact PKD to the TGN. Whereas C1a is sufficient to target a reporter protein to the TGN, mutation of serines 744/748 to alanines in the activation loop of intact PKD inhibits its localization to the TGN. Moreover, anti-phospho-PKD antibody, which recognizes only the activated form of PKD, recognizes the TGN-bound PKD. Thus, activation of intact PKD is important for binding to the TGN.

A specific immunoprecipitation assay for the protein kinase FA/glycogen synthase kinase 3.

A specific immunoprecipitation assay has been developed for the accurate determination of the kinase FA/GSK3 activity in crude cell preparations. The assay is based on the production and isolation of polyclonal peptide antibodies toward the C-terminus of the rat GSK3-alpha and GSK3-beta isoforms. The respective forms of the kinases are captured as active immunocomplexes with immobilized secondary antibodies and their kinase activity toward the synthetic peptide P-GS1 can be accurately measured. Immunoprecipitation with a mixture of the two peptide antibodies allows for the detection and estimation of the total kinase FA/GSK3 activity in cellular extracts, whereas the alpha-peptide antibody specifically detects and measures the GSK3-alpha isoform. The contribution of GSK3-beta in the total kinase FA/GSK3 activity of cell fractions can be calculated.

Platelet-derived growth factor stimulates protein kinase D through the activation of phospholipase Cgamma and protein kinase C.

Platelet-derived growth factor (PDGF) stimulates protein kinase D (PKD) in a time- and dose-dependent manner. We have used a series of PDGF receptor mutants that display a selective impairment of the binding of SH2-containing proteins (GTPase-activating protein, SHP-2, phospholipase Cgamma (PLCgamma), or phosphatidylinositol 3'-kinase (PI3K)) to show that Tyr-1021, the PLCgamma-binding site, is essential for PKD stimulation by PDGF in A431 cells. We next investigated whether any one of these four binding sites could mediate PKD activation in the absence of the other three sites. F5, a receptor mutant that lacks all four binding sites for GTPase-activating protein, PLCgamma, PI3K, and SHP-2, fails to activate PKD. A panel of single add-back mutants was used to investigate if any one of these four sites could restore signaling to PKD. Of the four sites, only the PLCgamma+ single add-back receptor restored PDGF-mediated activation of PKD, and only this add-back receptor produced diacylglycerol (DAG) in a PDGF-dependent manner. 1,2-Dioctanoyl-sn-glycerol, a membrane-permeant DAG analog, was found to be sufficient for activation of PKD. Taken together, these data indicate that PLCgamma activation is not only necessary, but also sufficient to mediate PDGF-induced PKD activation. Although the presence of a pleckstrin homology domain makes PKD a potential PI3K target, PKD was not stimulated by selective PI3K activation, and wortmannin, an inhibitor of PI3K, did not inhibit PDGF signaling to PKD. The activation of PKD by DAG or by the wild-type and PLCgamma+ add-back PDGF receptors was inhibited by GF109203X, suggesting a role for protein kinase C in the stimulation of PKD by PDGF. PDGF induced a time-dependent phosphorylation of PKD that closely correlated with activation. The PDGF-induced activation and phosphorylation of PKD were reversed by in vitro incubation of PKD with protein phosphatase 1 or 2A, indicating that PDGF signaling to PKD involves the Ser/Thr phosphorylation of PKD. Taken together, these results conclusively show that PDGF activates PKD through a pathway that involves activation of PLCgamma and, subsequently, protein kinase C.

Rapid stimulation of Ser/Thr protein kinases following treatment of Swiss 3T3 cells with bombesin. Involvement of casein kinase-2 in the signaling pathway of bombesin.

Treatment of quiescent Swiss 3T3 mouse fibroblasts with bombesin resulted in a rapid 6-8-fold stimulation of cytosolic Ser/Thr kinase activities toward the S6 peptide (RRLSSLR), myelin basic protein (MBP), and the G peptide (SPQPSRRGSESSEE). Anion exchange Mono Q chromatography resolved multiple S6 peptide- and G peptide kinase activities and two MBP kinase peaks. Both MBP- and several S6 peptide kinase peaks could be inactivated by PCSL (PP2A2) phosphatase action. This indicates that the bombesin-induced activation of these enzymes is mediated by a Ser/Thr phosphorylation event. The S6 peptide kinases as well as the two MBP kinases stimulated in response to bombesin are similar to those activated by epidermal growth factor in Swiss 3T3 fibroblasts which suggests that the early events of the signal transduction pathway mediated by these growth factors in Swiss 3T3 cells may converge in the activation of common Ser/Thr kinases. Bombesin, which acts as a sole mitogen for Swiss 3T3 fibroblasts, also produced a several-fold increase in the kinase activity toward the RRREEESEEE peptide, a specific substrate for CK-2. This kinase activity was heparin-sensitive and also measurable with the G peptide (SPQPSRRGSESSEE) and GS-1 peptide (YRRAAVPPSPSPSLSRHSSPHQSEDEE), which contain consensus sequences for phosphorylation by CK-2. The bombesin-stimulated CK-2 activity could not be measured in whole cytosols but was revealed by the anion exchange chromatography step. The activation of CK-2 was not reversed by PCSL phosphatase action. The implication of CK-2 in the signal transduction pathway of bombesin is discussed.