杜氏盐藻细胞质膜氧化还原系统

杜氏盐藻细胞质膜具的氧化ＮＡＤ（Ｐ）Ｈ,还原Ｆｅ（ＣＮ）＾３－６和Ｏ２的氧化还原系统。当Ｆｅ（ＣＮ）＾３－６浓度为０．６ｍｍｏｌ／Ｌ,氧化ＮＡＤＨ的Ｋｍ为９６μｍｏｌ／Ｌ,Ｖｍａｘ为１５９ｎｍｏｌ１０＾－８ｃｅｌｌｓｍｉｎ＾－１,最适ｐＨ为８．５。ＴｒｉｔｏｎＸ－１００可促进ＮＡＤＨ和Ｆｅ（ＣＮ）＾３－６的氧化还原活性。ＮＡＤＨ能促进藻细胞的氧吸收,最适ｐＨ为８．５。在无外源电子供体存在时,细胞质     

单宁酶的固定化及其在酯型儿茶素水解反应中的应用

采用自制的壳聚糖为载体对单宁酶（ＴＡ）固定化,ＴＡ与壳聚糖配比１：２．５,３０℃固定２ｈ,活力回收达２３．６％￣３３．１％;偶联效率为８４．９％￣８８．０％。固定化单宁酶（ＩＴＡ）的表观Ｋｍ值（以没食子酸丙酯为底物）为２２．２×１０＾－６ｍｏｌ／Ｌ,ＴＡ的Ｋｍ值（以没食子酸丙酯为底物）为１０×１０＾－６ｍｏｌ／Ｌ,ＴＡ和ＩＴＡ的最适反应温度分别为４０℃和５０℃;６０℃处理１５ｍｉｎ,残存活性分别为     

LHRH—A2及无机离子促进草鱼脑垂体离体分泌GH的初步研究

用培养瓶（皿）培养法研究ＬＨＲＨ－Ａ２、Ｃａ＾２＋、Ｋ＾＋对草鱼脑垂体器官分泌ＧＨ的影响。结果表明，１ｎｍｏｌ／Ｌ、１０ｎｍｏｌ／Ｌ、１００ｎｍｏｌ／Ｌ和１０００ｎｍｏｌ／Ｌ的ＬＨＲＨ－Ａ２都能显著促进ＧＨ的分泌；随着Ｃａ＾２＋浓度（０．１、１、３ｍｍｏｌ／Ｌ）的增高ＧＨ的分泌增强，在１ｍｏｌ／Ｌ和３ｍｍｏｌ／Ｌ Ｃａ＾２＋条件下的ＧＨ分泌水平显著高于在０．１ｍｍｏｌ／Ｌ Ｃａ＾２＋条件下的ＧＨ分     

鸭肫平滑肌肌球蛋白的提纯及其ATP酶性质的研究

从鸭肫肌肉中分离纯化了平滑肌肌球蛋白,并对平滑肌肌球蛋白分子的亚单位组成和平滑肌肌球蛋白的ＡＴＰ酶性质进行了分析研究。鸭肫平滑肌肌蛋白的Ｃａ＾２＋－ＡＴＰ酶活力与溶液的离子强度有关。在低于０．２０ｍｏｌ／Ｌ的ＫＣＬ浓度时,酶活力很低;大于０．３０ｍｏｌ／Ｌ的ＫＣＬ浓度时,酶活力较高,Ｃａ＾２＋－ＡＴＰ酶有两个最适ｐＨ值。Ｋ＾＋／ＥＤＴＡ－ＡＴＰ酶活力随ＫＣＬ浓度升高而增加。肌动蛋白激活的磷酸化肌球     

光氧化胁迫下几种植物叶片的超氧自由基产生速率和光合特性

以甲基藉精（ＭＶ）Ｏ－１ｍｍｏｌ／Ｌ在１５００μｍｏｌ ｍ＾－２ａ＾－１光下处理Ｃ３植物花生、水稻和Ｃ４植物玉米、甘蔗的叶圆片３０ｍｍ,Ｏ２＾２＋产生速率随ＭＶ浓度提高而加快ＭＶ浓度超过１０μｍｏｌ／Ｌ,光合放氧出现负植并持续增大。光氧化作用降低叶绿素荧光参数ＦＶ／Ｆｍ,ΦＰＳⅡ和ｑｐ,而ｑＮ则或提高（Ｃ３植物,ＭＶ１０μｍｏｌ／Ｌ）或几平下）。热耗散系数ＫＤ的变化与ＱＮ相似。秘Ｃ４植物相比,Ｃ３     

亚硝酸盐对培养心肌细胞周期的影响

本文用流式细胞仪测定了ＮａＮＯ２对体外培养的Ｗｉｓｔａｒ乳鼠心肌细胞周期的影响。结果表明,１０＾－６ｍｏｌ／Ｌ ＮａＮＯ２引起Ｓ期细胞明显减少（Ｐ〈０．０５）;１０＾－８ｍｏｌ／Ｌ ＮａＮＯ２对其 显著（Ｐ〉０．０５）。应用「３Ｈ」ＴｄＲ掺入法测定了ＮａＮＯ２对心肌细胞增殖的作用。实验发现,１０＾－６ｍｏｌ／Ｌ ＮａＮＯ２明显抑制细胞增殖,而１０＾－９－１０＾７ｍｏｌ／Ｌ的ＮａＮＯ２则促进细胞增殖     

高分子量和低分子量尿激酶的分离纯化及动力学性质研究

人尿激酶粗品经苯甲脒亲和柱纯化和Ｐｒｏｔｅｉｎ－ＰａｋＳＰ柱分离后,得到两种分子量的尿激酶（ＵＫ）,即高分子量尿激酶（ＨＵＫ）和低分子量尿激酶（ＬＵＫ）,采用民斯亮蓝法测定蛋白质浓度,纤维蛋白板法测定活力,测得ＨＵＫ比活为２．９×１０＾５ＩＵ／ｍｇ蛋白,ＬＵＫ为３．５１０＾５ＩＵ／ｍｇ蛋白,活力回收为７０％以上,经ＳＤＳ－ＰＡＧＥ鉴定,ＨＵＫ和ＬＵＫ均呈单一条带,分子量分别为５４ｋＤ和３３ｋＤ,Ｈ     

大肠杆菌精氨酰－tRNA合成酶变种ArgRS381KA的基本性质

本文研究了Ｌｙｓ３８１变为Ａｌａ的精氨酰－ｔＲＮＡ合成酶（ＡｒｇＲＳ）变种ＡｒｇＲＳ３８１ＫＡ的最适ｐＨ和稳态动力学性质;比较了此酶与天然酶ＡｒｇＲＳ的荧光光谱性质和热稳定性。实验结果表明ＡｒｇＲＳ３８１ＫＡ的氨酰化活力和ＡＴＰ￣ＰＰｉ交换活力的最适ｐＨ分别为８．０和７．０,与天然酶相同;ＡｒｇＲＳ３８１ＫＡ的氨酰化活力对精氨酸、ＡＴＰ和ｔＲＮＡＡｒｇ的Ｋｍ分别为１２μｍｏｌ／Ｌ、０．３ｍｍｏｌ／Ｌ和１．１μｍｏｌ／Ｌ,Ｖｍａｘ为１６０００Ｕ／ｍｇ,ｋｃａｔ为１６ｓ－１;ＡＴＰ￣ＰＰｉ交换活力对精氨酸、ＡＴＰ和ＰＰｉ的Ｋｍ分别为９２．９μｍｏｌ／Ｌ、０．８５ｍｍｏｌ／Ｌ和８０．１μｍｏｌ／Ｌ,Ｖｍａｘ为２８０００～３００００Ｕ／ｍｇ,ｋｃａｔ为３２ｓ－１．ＡｒｇＲＳ３８１ＫＡ的荧光激发光谱和发射光谱与ＡｒｇＲＳ基本相同。热失活速度比天然酶慢。     

运动对大鼠血小板L—精氨酸转运的影响

本工作在游泳大鼠模型上,观察血小板Ｌ－精氨酸（Ｌ－Ａｒｇ）转运特征,并观察凝血酶和ＰＡＦ对血小板Ｌ－Ａｒｇ转运的影响。结果发现,运动大鼠血小板Ｌ－Ａｒｇ转运明显高于未运动对照大鼠,表现在高亲和性最大转运速率（Ｖｍａｘ）明显增高（５０．５６±３．２７ｐｍｏｌ／１０８ｖｓ４５．８４±２．３６ｐｍｏｌ／１０８血小板／ｍｉｎ。Ｐ＜０．０５）,米氏常数亦显著增加（２．１４±０．２３μｍｏｌ／Ｌｖｓ１．４６±０．１３μｍｏｌ／Ｌ,Ｐ＜０．０１）。应用刺激剂凝血酶和ＰＡＦ诱导运动大鼠血小板Ｌ－Ａｒｇ转运速率增加的幅度明显高于未运动对照大鼠（Ｐ＜０．０１）。实验结果表明,运动能增强血小板转运Ｌ－Ａｒｇ的效率。提示,运动可能促进血小板一氧化氮（ＮＯ）生成,抑制血小板聚集,防治血管栓塞性疾病     

抗旱性不同的两个大豆品种对外源H2O2的响应

两个品种的大豆叶圆片经１０＾－４ｍｏｌ／Ｌ和１０＾－３ｍｏｌ／Ｌ的Ｈ２Ｏ２处理１２ｈ后,超氧化岐化酶（ＳＯＤ）、过氧化氢酶（ＣＡＴ）与谷胱甘肽还原酶（ＧＲ）活性明显增加,但１０＾－２ｍｏｌ／Ｌ的Ｈ２Ｏ２处理却使这些酶活性降低。抗旱性较强的大豆品种小粒豆１号较抗旱性较弱的鲁豆４号能维持较高的叶绿素含量和较高的ＳＯＤ、ＣＡＴ及ＧＲ活性,对Ｈ２Ｏ２的抗性较强。５０μｍｏｌ／Ｌ的亚胺环已酮（ＣＨＭ）能消除     

Differential Regulation of Focal Adhesion Kinase and Mitogen-Activated Protein Kinase Tyrosine Phosphorylation During Insulin-Like Growth Factor-I-Mediated Cytoskeletal Reorganization

Abstract: In SH-SY5Y human neuroblastoma cells, insulin-like growth factor (IGF)-I mediates membrane ruffling and growth cone extension. We have previously shown that IGF-I activates the tyrosine phosphorylation of focal adhesion kinase (FAK) and extracellular signal-regulated protein kinase (ERK) 2. In the current study, we examined which signaling pathway underlies IGF-I-mediated FAK phosphorylation and cytoskeletal changes and determined if an intact cytoskeleton was required for IGF-I signaling. Treatment of SH-SY5Y cells with cytochalasin D disrupted the actin cytoskeleton and prevented any morphological changes induced by IGF-I. Inhibitors of phosphatidylinositol 3-kinase (PI 3-K) blocked IGF-I-mediated changes in the actin cytoskeleton as measured by membrane ruffling. In contrast, PD98059, a selective inhibitor of ERK kinase, had no effect on IGF-I-induced membrane ruffling. In parallel with effects on the actin cytoskeleton, cytochalasin D and PI 3-K inhibitors blocked IGF-I-induced FAK tyrosine phosphorylation, whereas PD98059 had no effect. It is interesting that cytochalasin D did not block IGF-I-induced ERK2 tyrosine phosphorylation. Therefore, it is likely that FAK and ERK2 tyrosine phosphorylations are regulated by separate pathways during IGF-I signaling. Our study suggests that integrity as well as dynamic motility of the actin cytoskeleton mediated by PI 3-K is required for IGF-I-induced FAK tyrosine phosphorylation, but not for ERK2 activation.     

Role of the actin cytoskeleton in angiotensin II signaling in human vascular smooth muscle cells

Angiotensin II (Ang II) regulates vascular smooth muscle cell (VSMC) function by activating signaling cascades that promote vasoconstriction, growth, and inflammation. Subcellular mechanisms coordinating these processes are unclear. In the present study, we questioned the role of the actin cytoskeleton in Ang II mediated signaling through mitogen-activated protein (MAP) kinases and reactive oxygen species (ROS) in VSMCs. Human VSMCs were studied. Cells were exposed to Ang II (10-7 mol/L) in the absence and presence of cytochalasin B (10-6 mol/L, 60 min), which disrupts the actin cytoskeleton. Phosphorylation of p38MAP kinase, JNK, and ERK1/2 was assessed by immuno blotting. ROS generation was measured using the fluoroprobe chloromethyl-2',7'-dichlorodihydrofluorescein diacetate (4 micromol/L). Interaction between the cytoskeleton and NADPH oxidase was determined by evaluating the presence of p47phox in the Triton X-100 insoluble membrane fraction. Ang II significantly increased phosphorylation of p38MAP kinase, JNK, and ERK1/2 (two- to threefold above control, p < 0.05). Cytochalasin B pretreatment attenuated p38MAP kinase and JNK effects (p < 0.05) without altering ERK1/2 phosphorylation. ROS formation, which was increased in Ang II stimulated cells, was significantly reduced by cytochalasin B (p < 0.01). p47phox, critically involved in NADPH oxidase activation, colocalized with the actin cytoskeleton in Ang II stimulated cells. Our data demonstrate that Ang II mediated ROS formation and activation of p38MAP kinase and JNK, but not ERK1/2, involves the actin cytoskeleton in VSMCs. In addition, Ang II promotes interaction between actin and p47phox. These data indicate that the cytoskeleton is involved in differential MAP kinase signaling and ROS generation by Ang II in VSMCs. Together, these studies suggest that the cytoskeleton may be a central point of crosstalk in growth- and redox-signaling pathways by Ang II, which may be important in the regulation of VSMC function.     

Protein kinase C-mediated tyrosine phosphorylation of paxillin and focal adhesion kinase requires cytoskeletal integrity and is uncoupled to mitogen-activated protein kinase activation in human hepatoma cells

Treatment of cultured human hepatoma HepG2 cells with the protein kinase C (PKC) activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), results in an increase in tyrosine phosphorylation of several proteins, including the focal adhesion kinase (FAK) and paxillin using anti-phosphotyrosine Western blotting and immunoprecipitation. However, when cells are in suspension or in the presence of cytochalasin D which disrupts the intracellular network of actin microfilaments, TPA loses its ability to stimulate tyrosine phosphorylation of FAK and paxillin but it still activates mitogen-activated protein kinase (MAPK) and induces PKC translocation from cytosol to the membrane in HepG2 cells. On the other hand, PD98059, a specific inhibitor of mitogen-activated protein kinase kinase, blocks TPA-induced MAPK activation but has no effect on TPA-induced tyrosine phosphorylation. Our findings suggest that TPA-induced tyrosine phosphorylation of FAK and paxillin in human hepatoma cells is PKC dependent and requires the integrity of the cell cytoskeleton but is uncoupled to the signal transduction pathway of PKC leading to the translocation of PKC and MAPK activation.     

Reversal effect of specific inhibitors of extracellular-signal regulated protein kinase pathway on P-glycoprotein mediated vincristine resistance of L1210 cells

Effect of specific inhibitors of extracellular-signal regulated protein kinase (ERK) pathway, PD98059 and U0126, on P-glycoprotein (Pgp)-mediated vincristine resistance of L1210/VCR cells was investigated. Both test inhibitors significantly reduced the survival of L1210/VCR cells in the presence of vincristine and this was associated with a decrease of LC50 values to vincristine from 2.65+/-0.43 to 0.67+/-0.28 micromol/l and to 0.69+/-0.09 micromol/l after treatment with 50 micromol/l PD98059 and 25 micromol/l UO126, respectively. Moreover, the effects of PD98059 are connected also with an increased intracellular accumulation of radiolabeled vincristine in resistant L1210/VCR cells in concentration dependent manner. The results of this study demonstrate that inhibitors of ERK signaling pathway are reversal agents of vincristine resistance in L1210/VCR cells. The precise mechanism of PD98059 and U0126 action in modulation of MDR is not resolved yet, but the role of ERK-mediated phosphorylation cascade could be considered.     

Glutamate induces focal adhesion kinase tyrosine phosphorylation and actin rearrangement in heterologous mGluR1-expressing CHO cells via calcium/calmodulin signaling

Group 1 metabotropic glutamate receptors (mGluR1 and mGluR5) stimulate phospholipase C (PLC) and lead to mobilization of intracellular Ca(2+) and activation of protein kinase C (PKC). In this investigation, using heterologous receptor-expressing Chinese hamster ovary (CHO) cells, we showed that stimulation of mGluR1 or mGluR5 with glutamate rapidly increases tyrosine phosphorylation of focal adhesion kinase (FAK) (maximum at 1-3 min) in a dose-dependent manner (half-maximal responses at approximately 2 microM). In mGluR1-expressing cells, the glutamate-induced increase of FAK tyrosine phosphorylation was blocked by not only the PLC inhibitor, U73122, but also depletion of intracellular Ca(2+) and effectively abrogated by calmodulin (CaM) inhibitors, calmidazolium and fluphenazine. However, neither the PKC inhibitor, GF109203X, nor the CaM kinase II inhibitor, KN-62, inhibited glutamate-stimulated FAK tyrosine phosphorylation. Stimulation of mGluR1 caused a marked increase in actin stress fiber formation. Importantly, this actin rearrangement was prevented by the CaM inhibitor, but not by the PKC inhibitor and is thus in a good agreement with the signaling cascade of the mGluR1-FAK pathway. These results suggest that the Ca(2+)/CaM signaling and its downstream FAK tyrosine phosphorylation play an important role in cellular function of mGluR1.     

Angiotensin II activation of focal adhesion kinase and pp60c-Src in relation to mitogen-activated protein kinases in hepatocytes

We have investigated signaling pathways leading to angiotensin II (Ang II) activation of mitogen-activated protein kinase (MAPK) in hepatocytes. MAPK activation by Ang II was abolished by the Ang II type 1 (AT1) receptor antagonist losartan, but not by the Ang II type 2 (AT2) receptor antagonist PD123319. Ang II (100 nM) induced a rapid phosphorylation of Src (peak approximately 2 min) and focal adhesion kinase (FAK, peak approximately 5 min) followed by a decrease to basal levels in 30 min. An increased association between FAK and Src in response to Ang II was detected after 1 min, which declined to basal levels after 30 min. Treatment with the Src kinase inhibitor PP-1 inhibited FAK phosphorylation. Downregulation of PKC, intracellular Ca2+ chelator BAPTA or inhibitors of PKC, Src kinase, MAPK kinase (MEK), Ca2+/calmodulin dependent protein kinase, phosphatidylinositol 3-kinase all blocked Ang II-induced MAPK phosphorylation. In contrast to other cells, there was no evidence for the role of EGF receptor transactivation in the activation of MAPK by Ang II. However, PDGF receptor phosphorylation is involved in the Ang II stimulated MAPK activation. Furthermore, Src/FAK and Ca/CaM kinase activation serve as potential links between the Ang II receptor and MAPK activation. These studies offer insight into the signaling network upstream of MAPK activation by AT1 receptor in hepatocytes.     

Activation of focal adhesion kinase by protein kinase C epsilon in neonatal rat ventricular myocytes

Focal adhesion kinase (FAK) is a nonreceptor protein tyrosine kinase critical for both cardiomyocyte survival and sarcomeric assembly during endothelin (ET)-induced cardiomyocyte hypertrophy. ET-induced FAK activation requires upstream activation of one or more isoenzymes of protein kinase C (PKC). Therefore, with the use of replication-defective adenoviruses (Adv) to overexpress constitutively active (ca) and dominant negative (dn) mutants of PKCs, we examined which PKC isoenzymes are necessary for FAK activation and which downstream signaling components are involved. FAK activation was assessed by Western blot analysis with an antibody specific for FAK autophosphorylated at Y397 (Y397pFAK). ET (10 nmol/l; 2-30 min) resulted in the time-dependent activation of FAK which was inhibited by chelerythrine (5 micromol/l; 1 h pretreatment). Adv-caPKC epsilon, but not Adv-caPKC delta, activated FAK compared with a control Adv encoding beta-galactosidase. Conversely, Adv-dnPKC epsilon inhibited ET-induced FAK activation. Y-27632 (10 micromol/l; 1 h pretreatment), an inhibitor of Rho-associated coiled-coil-containing protein kinases (ROCK), prevented ET- and caPKC epsilon-induced FAK activation as well as cofilin phosphorylation. Pretreatment with cytochalasin D (1 micromol/l, 1 h pretreatment) also inhibited ET-induced Y397pFAK and cofilin phosphorylation and caPKC epsilon-induced Y397pFAK. Neither inhibitor, however, interfered with ET-induced ERK1/2 activation. Finally, PP2 (50 micromol/l; 1 h pretreatment), a highly selective Src inhibitor, did not alter basal or ET-induced Y397pFAK. PP2 did, however, reduce basal and ET-induced phosphorylation of other sites on FAK, namely, Y576, Y577, Y861, and Y925. We conclude that the ET-induced signal transduction pathway resulting in downstream Y397pFAK is partially dependent on PKC epsilon, ROCK, cofilin, and assembled actin filaments, but not ERK1/2 or Src.     

Activation of MAPK by modified low-density lipoproteins in vascular smooth muscle cells.

A high concentration of circulating low-density lipoproteins (LDL) is a major risk factor for atherosclerosis. Native LDL and LDL modified by glycation and/or oxidation are increased in diabetic individuals. LDL directly stimulate vascular smooth muscle cell (VSMC) proliferation; however, the mechanisms remain undefined. The extracellular signal-regulated kinase (ERK) pathway mediates changes in cell function and growth. Therefore, we examined the cellular effects of native and modified LDL on ERK phosphorylation in VSMC. Addition of native, mildly modified (oxidized, glycated, glycoxidized) and highly modified (highly oxidized, highly glycoxidized) LDL at 25 microg/ml to rat VSMC for 5 min induced a fivefold increase in ERK phosphorylation. To elucidate the signal transduction pathway by which LDL phosphorylate ERK, we examined the roles of the Ca(2+)/calmodulin pathway, protein kinase C (PKC), src kinase, and mitogen-activated protein kinase kinase (MEK). Treatment of VSMC with the intracellular Ca(2+) chelator EGTA-AM (50 micromol/l) significantly increased ERK phosphorylation induced by native and mildly modified LDL, whereas chelation of extracellular Ca(2+) by EGTA (3 mmol/l) significantly reduced LDL-induced ERK phosphorylation. The calmodulin inhibitor N-(6-aminohexyl)-1-naphthalenesulfonamide (40 micromol/l) significantly decreased ERK phosphorylation induced by all types of LDL. Downregulation of PKC with phorbol myristate acetate (5 micromol/l) markedly reduced LDL-induced ERK phosphorylation. Pretreatment of VSMC with a cell-permeable MEK inhibitor (PD-98059, 40 micromol/l) significantly decreased ERK phosphorylation in response to native and modified LDL. These findings indicate that native and mildly and highly modified LDL utilize similar signaling pathways to phosphorylate ERK and implicate a role for Ca(2+)/calmodulin, PKC, and MEK. These results suggest a potential link between modified LDL, vascular function, and the development of atherosclerosis in diabetes.     

Cytoskeletal and Phosphoinositide Requirements for Muscarinic Receptor Signaling to Focal Adhesion Kinase and Paxillin

Abstract: The mechanism whereby agonist occupancy of muscarinic cholinergic receptors elicits an increased tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin has been examined. Addition of oxotremorine-M to SH-SY5Y neuroblastoma cells resulted in rapid increases in the phosphorylation of FAK ( t _1/2 = 2 min) and paxillin that were independent of integrin-extracellular matrix interactions, cell attachment, and the production of phosphoinositide-derived second messengers. In contrast, the increased tyrosine phosphorylations of FAK and paxillin were inhibited by inclusion of either cytochalasin D or mevastatin, agents that disrupt the cytoskeleton. Furthermore, phosphorylation of FAK and paxillin could be prevented by addition of either wortmannin or LY-294002, under conditions in which the synthesis of phosphatidylinositol 4-phosphate was markedly attenuated. These results indicate that muscarinic receptor-mediated increases in the tyrosine phosphorylation of FAK and paxillin in SH-SY5Y neuroblastoma cells depend on both the maintenance of an actin cytoskeleton and the ability of these cells to synthesize phosphoinositides.     

Dissociation of mitogen-activated protein kinase activation from p125 focal adhesion kinase tyrosine phosphorylation in Swiss 3T3 cells stimulated by bombesin, lysophosphatidic acid, and platelet-derived growth factor.

The experiments presented here were designed to examine the contribution of p125 focal adhesion kinase (p125FAK) tyrosine phosphorylation to the activation of the mitogen-activated protein kinase cascade induced by bombesin, lysophosphatidic acid (LPA), and platelet-derived growth factor (PDGF) in Swiss 3T3 cells. We found that tyrosine phosphorylation of p125FAK in response to these growth factors is completely abolished in cells treated with cytochalasin D or in cells that were suspended in serum-free medium for 30 min. In marked contrast, the activation of p42mapk by these factors was independent of the integrity of the actin cytoskeleton and of the interaction of the cells with the extracellular matrix. The protein kinase C inhibitor GF 109203X and down-regulation of protein kinase C by prolonged pretreatment of cells with phorbol esters blocked bombesin-stimulated activation of p42mapk, p90rsk, and MAPK kinase-1 but did not prevent bombesin-induced tyrosine phosphorylation of p125FAK. Furthermore, LPA-induced p42mapk activation involved a pertussis toxin-sensitive guanylate nucleotide-binding protein, whereas tyrosine phosphorylation of p125FAK in response to LPA was not prevented by pretreatment with pertussis toxin. Finally, PDGF induced maximum p42mapk activation at concentrations (30 ng/ml) that failed to induce tyrosine phosphorylation of p125FAK. Thus, our results demonstrate that p42mapk activation in response to bombesin, LPA, and PDGF can be dissociated from p125FAK tyrosine phosphorylation in Swiss 3T3 cells.