aFGF对人脐静脉内皮细胞TPK、PKC活性及Ca2+浓度的影响

为了观察酸性成纤维细胞生长因子 ( acidic fibroblast growth factor,a FGF)与人脐静脉内皮细胞 ( human umbilical vein endothelial cell,HUVEC)膜上特异受体结合后引起的细胞内信号转导途径 ,探讨 a FGF导致细胞增殖的机理 ,经 Scatchard曲线分析人脐静脉内皮细胞膜受体性质 .以不同浓度的 a FGF处理人脐静脉内皮细胞 ,利用 [γ- 3 2 P]ATP参入外源性底物的方法测定受体的酪氨酸蛋白激酶 ( tyrosine protein kinase,TPK)及蛋白激酶 C( protein kinase C,PKC)的活性 ;用 Fura-2 /AM为荧光指示剂测定 [Ca2 ]i.结果显示 :Scatchard曲线证明 a FGF与 HUVEC膜受体特异结合呈一条曲线 ,即受体为一种结合位点 ,Kd 为 3.6× 1 0 -10～ 9.6× 1 0 -10 mol/L,每个细胞受体数为2 70 90 .随着 a FGF浓度增加 ,TPK及 PKC活性随之升高 .当 a FGF浓度为 1 .1 2 mg/L时 ,a FGF处理组的 TPK活性是对照组的 3倍 ;膜 PKC活性是对照组 3.4倍 ,胞浆 PKC活性是对照组的 1 .87倍 .胞浆 [Ca2 ]是对照组的 3倍 .结果指出 :该细胞中 a FGF受体具有 TPK活性 .TPK激活后进一步促进蛋白质和酶磷酸化级联反应 ,而使 PKC活性及 [Ca2 ]i 升高 ,即 PKC和 Ca2 为 TPK的下游信号分子 ,进一步促进基因表达增加 ,导致细胞增殖 .     

aFGF对人脐静脉内皮细胞TPK、PKC活性及Ca~(2+)浓度的影响

为了观察酸性成纤维细胞生长因子 ( acidic fibroblast growth factor,a FGF)与人脐静脉内皮细胞 ( human umbilical vein endothelial cell,HUVEC)膜上特异受体结合后引起的细胞内信号转导途径 ,探讨 a FGF导致细胞增殖的机理 ,经 Scatchard曲线分析人脐静脉内皮细胞膜受体性质 .以不同浓度的 a FGF处理人脐静脉内皮细胞 ,利用 [γ- 3 2 P]ATP参入外源性底物的方法测定受体的酪氨酸蛋白激酶 ( tyrosine protein kinase,TPK)及蛋白激酶 C( protein kinase C,PKC)的活性 ;用 Fura-2 /AM为荧光指示剂测定 [Ca2 + ]i.结果显示 :Scatchard曲线证明 a FGF与 HUVEC膜受体特异结合呈一条曲线 ,即受体为一种结合位点 ,Kd 为 3.6× 1 0 -10～ 9.6× 1 0 -10 mol/L,每个细胞受体数为2 70 90 .随着 a FGF浓度增加 ,TPK及 PKC活性随之升高 .当 a FGF浓度为 1 .1 2 mg/L时 ,a FGF处理组的 TPK活性是对照组的 3倍 ;膜 PKC活性是对照组 3.4倍 ,胞浆 PKC活性是对照组的 1 .87倍 .胞浆 [Ca2 + ]是对照组的 3倍 .结果指出 :该细胞中 a FGF受体具有 TPK活性 .TPK激活后进一步促进蛋白质和酶磷酸化级联反应 ,而使 PKC活性及 [Ca2 + ]i 升高 ,即 PKC和 Ca2 + 为 TPK的下游信号分子 ,进一步促进基因表达增加 ,导致细胞增殖 .     

维甲酸对人肝癌细胞磷脂酰胆碱专一性磷脂酶D的作用

为了解细胞信号转导与细胞分化间的关系,研究了诱导分化剂全反式视黄酸(ATRA)和13顺视黄酸(13 cis-RA)对7721人肝癌细胞中磷脂酰胆碱专一性磷脂酶D(PC-PLD)的影响。发现ATRA和13 cis-RA除能抑制7721细胞生长,并在形态上向正常方向分化外,分别在第2或第4天使膜结合性PC-PLD的比活力升高,用每瓶细胞的总活力计算,ATRA的作用在第2天也高于13 cis-RA,但13 cis-RA在第4天的效应却高于ATRA,说明13 cis-RA较ATRA的效应滞后。每天更换培养液的条件较不更换时细胞生长速度较快,且更能引起PC-PLD比活力的上升,提示新鲜培养液中可能存在促进生长和增强维甲酸升高PC-PLD的化合物。ATRA在第2天对PC-PLD比活力的作用高于第4天,可能由于第4天细胞增殖加快,细胞中蛋白质含量上升,以至使以蛋白含量计算的酶比活力下降。进一步研究维甲酸使膜结合性PC-PLD升高与蛋白激酶的关系,发现ATRA不论在第2天和第4天均使膜结合性和胞液中蛋白激酶C(PKC)和酪氨酸蛋白激酶(TPK)的比活力下降,说明ATRA使膜结合性PC-PLD活力的升高不是通过PKC 或TPK对PC-PLD的激活作用来实现,其机理有待进一步研究。对维甲酸引起PC-PLD升高的生物学意义作了讨论。     

蛋白激酶与细胞分化—两种分化诱导剂对酪氨酸蛋白激酶的抑制

在报道视黄酸(RA)是人肝癌细胞株SMMC-7721分化诱导剂的基础上,本文继续报道8-溴-环磷酸腺苷对该细胞也有分化诱导作用,两者都抑制细胞的增殖,降低γ-谷氨酰转肽酶(γ-GT)比活力和升高(ALP)碱性磷酸酶的比活力。在10μmol/LRA和0.5mmol/L-8-Br-cAMP处理细胞1、3、5天后,胞液和膜性组分中的酪氨酸蛋白激酶(TPK)的比活力均降低,其中RA对胞液TPK的作用在早期较明显,约降低30％,而对膜性TPK的影响则随培养天数而逐渐增加,至第5天下降达50％以上。8Br-cAMP则相反,对胞浆TPK的抑制主要发生在3天以后;约抑制43—53％,而对膜性组分则抑制率逐日降低,在第一天较为明显。因TPK是一个细胞增殖恶变的标志,故RA和8-溴-cAMP对TPK的抑制进一步证明这两种分化诱导剂对SMMC-7721细胞的逆转作用。     

细胞周期和骨架在CNE-2Z细胞凋亡中的变化

采用DNA电泳、PI染色流式细胞仪(FCM)分析和激光共聚焦显微镜(LCM)观察, 检测了蛋白激酶C(PKC)抑制剂诱导CNE-2Z细胞凋亡时细胞周期和骨架的改变. PKC抑制剂staurospoine(ST)、sphingosine(SS), 终浓度分别为1×10^-6 mol/L和4×10^-5 mol/L, 诱导细胞24 h.结果发现处理组细胞均有典型的DNA亚二倍体峰, DNA电泳有梯状图谱; 细胞周期百分比SS组较对照组S期增加及G1期减少明显(P＜0.05); ST组G2期增加、G1和S期显著减少(P＜0.01). 对照组细胞染色质分布均匀; 胞质微丝呈细颗粒状, 均匀分布. 诱导细胞染色质碎裂呈不规则缺损; 胞质微丝散乱, 颗粒粗大, 排列不均. 结果表明, SS、ST可诱导CNE-2Z细胞凋亡, 细胞周期和骨架在细胞凋亡时, 均发生了明显改变.     

青藤碱对家兔主动脉血管平滑肌细胞内游离钙浓度及蛋白激酶C的影响

观测青藤碱对培养家兔血管平滑肌细胞内游离钙浓度及正常和缺血缺氧刺激下蛋白激酶C（PKC）活性的影响。方法：Fura-2／AM作Ca^2＋指示剂,检测青藤碱对培养家兔主动脉血管平滑肌细胞静息Ca^2＋浓度及去甲肾上腺素,高K^＋,咖啡因刺激作用下的改变,并与钙拮抗剂维拉帕米进行对照研究;复制血管平滑肌细胞缺血缺氧模型,液闪仪测定PKC活性。结果：青藤碱剂量依赖性抑制高K^＋去极化引起[Ca^2＋]i升高,青藤碱10×10^-6mol.L^-1、3×10^-5mol.L^-1、10^-4mol.L^-1,对NE通过受体介导引起的[Ca^2＋]i增高也有明显抑制。但对静息状态下及咖啡因刺激的血管平滑肌细胞[Ca^2＋]i无明显影响。正常时,青藤碱处理后血管平滑肌细胞胞浆、胞膜PKC活性均升高;缺血缺氧状态下,胞浆PKC活性升高,但胞膜PKC活性降低,青藤碱处理后胞浆PKC活性下降,胞膜PKC活性上升。结论：青藤碱可能抑制血管平滑肌细胞电压依赖性钙通道和受体操纵性钙通道,降低细胞内游离钙水平。调节缺血缺氧条件下血管平滑肌细胞PKC活性。     

IL27RA对EBV感染的鼻咽癌细胞TRAF1/2表达的调控及其生物学效应

EB病毒(Epstein-Barr virus,EBV)感染是鼻咽癌(Nasopharyngeal carcinoma,NPC)最主要的危险因素,主要通过肿瘤坏死因子受体相关分子-1/2(Tumor necrosis factor receptor-associated factor-1/2,TRAF1/2)发挥促癌作用,为探究白介素27受体亚基α(Interleukin 27 receptorα,IL27RA)表达与NPC细胞EBV感染的关系及其生物学效应,本研究采用肿瘤基因组计划(The Cancer Genome Atlas,TCGA)数据库在NPC组织中筛选EBV感染相关信号分子TRAF1/2的潜在相互作用分子,培养携带EBV的NPC细胞株HK-1和C666-1及未携带EBV的NPC细胞株CNE-1及CNE-2,实时荧光定量PCR技术(RT-qPCR)及蛋白质印迹技术(Western Blot)检测IL27RA mRNA及蛋白表达,慢病毒介导细胞转染技术外源性干扰HK-1和C666-1细胞IL27RA的表达,CCK-8检测细胞增殖能力的变化情况,Transwell实验检测细胞侵袭能力的变化情况。结果显示,NPC组织中存在与TRAF1/2表达均显著正相关的分子IL27RA(相关系数R分别为0.61及0.69,P均小于0.001),同时IL27RA在NPC组织中高表达(P0.001),HK-1和C666-1中IL27RA mRNA及蛋白的表达水平显著高于CNE-1及CNE-2细胞(P0.01),干扰HK-1和C666-1细胞IL27RA表达后,TRAF1及TRAF2 mRNA及蛋白表达显著下调(P0.01),且细胞增殖及转移能力均显著减弱(P0.01)。本研究提示,干扰IL27RA表达可显著抑制携带EBV的NPC细胞TRAF1/2的表达及细胞增殖转移能力,IL27RA有望成为NPC新的分子靶标或标志物。     

EBV阳性与阴性NPC细胞中AKR1B10的差异表达及生物学意义

研究EB病毒（Epstein-Barr virus,EBV）阳性与阴性鼻咽癌（Nasopharyngeal carcinoma,NPC）细胞中醛酮还原酶家族1成员B10(AKR1B10)的差异表达及生物学意义。收集NPC组织并检测EBV感染情况及AKR1B10表达水平，比较EBV阳性与阴性NPC组织中AKR1B10表达水平的差异；培养EBV阳性的NPC细胞株HK-1和C666-1、EBV阴性的NPC细胞株CNE-1及CNE-2，检测AKR1B10的表达水平。HK-1和C666-1进行分组，给予10μmol/L、20μmol/L AKR1B10抑制剂处理，20μmol/L AKR1B10抑制剂联合对照溶剂或20μmol/L β-catenin激动剂处理，检测细胞增殖水平、侵袭数目及c-myc、MMP2、MMP9的mRNA表达水平，AKR1B10、总β-连环蛋白（β-catenin）、核β-catenin的蛋白表达水平。结果显示HK-1和C666-1细胞中AKR1B10的蛋白表达水平高于CNE-1及CNE-2;10μmol/L、20μmol/L AKR1B10抑制剂组HK-1和C666-1...     

两种酪氨酸蛋白激酶活性在主动脉平滑肌细胞增殖周期中的动态变化

本文以人工合成的多肽PGAT 为底物鉴定了培养的家兔ASMC 膜性TPK。发现Mg~(2+)和Mn~(2+)对ASMC 胞浆膜性TPK 和核膜性TPK 的激活作用有两点不同:(1)它们对前者的最适激活浓度高于后者;(2)对胞浆膜性TPK,Mn~(2+)最大激活效应大于Mg~(2+)而对核膜性TPK,Mn~(2+)则低于Mg~(2+)。这两种TPK活性在其G_1期的变化特点是:胞浆膜性TPK最高活性出现在G_1晚期(9 h),核膜性TPK最高活性则出现在G_1早期(3 h)。     

乙型肝炎病毒(HBV)体内外对单个核细胞白细胞介素-1和白细胞介素-2诱生活性影响的研究

本研究用PAP法、胸腺细胞增殖法、脾细胞增殖法,分别检测16例体外HBV感染的骨髓单个核细胞与16例慢性乙型肝炎患者体内感染的骨髓单个核细胞(MNCs)中的HBcAg和白细胞介素-1(IL-1)、白细胞介素-2(IL-2)的诱生活性(以△cpm值表示)。结果显示,体外HBV感染组与体内HBV感染组骨髓MNCs中HBcAg检出率分别为50％和43.7％。本实验结果表明,HBV在体外感染骨髓MNCs,且与体内自然感染相符,但光镜下未观察到致细胞病变效应(CPE)。体外感染组与体内感染组IL-I和IL-2活性均较对照组明显下降(P<0.01)。且细胞中HBcAg检出阳性者较阴性者下降更为明显(P<0.01)。IL-1和IL-2诱生活性降低与HBV侵染免疫细胞及其在细胞内复制有密切关系,从而提示,IL-1和IL-2降低可能影响HBV的清除而引起慢性化过程。     

蛋白激酶C对鼻咽癌细胞c－myc，c－fos表达的影响

用蛋白激酶Ｃ（ＰＫＣ）抑制剂Ｓｔａｕｒｏｓｐｏｒｉｎｅ（ＳＴ,抑制催化亚基）与Ｓｐｈｉｎｇｏｓｉｎｅ（ＳＳ,抑制调节亚基）处理人鼻咽癌细胞系ＣＮＥ－２Ｚ,经点印迹后扫描定量和免疫细胞化学检测ｃ－ｍｙｃ、ｃ－ｆｏｓ表达及其分布。结果发现：（１）ｃ－ｍｙｃ蛋白：主要分布于胞浆,４０．７％的细胞核与胞浆均为阳性;经ＳＳ或ＳＴ处理后,表达明显减弱,且核阳性率分别为１７．３％与２３．３％。扫描定量在ＳＳ组为对照组的６０％±２５．７％（Ｐ＜０．０５）,ＳＴ组为对照组的５５％±２５．９％（Ｐ＜０．０５）。（２）Ｃ－ｆｏｓ蛋白：主要分布于胞浆,２９．４％的细胞核与胞浆均为阳性,经ＳＳ或ＳＴ处理后,表达明显减弱,且核阳性率分别为９％与１０．２％。扫描定量ＳＳ组为对照组的５８．６％±２５％（Ｐ＜０．０５）,ＳＴ组为对照组的５９．７％±２６．２％（Ｐ＜０．０５）。结果表明：使用ＰＫＣ抑制剂后,两种核癌基因产物量均有不同程度的减少,并且存在细胞内分布的改变,特别是其发挥效应的核内表达明显减少。结合我们以前所发现的ＰＫＣ抑制剂明显抑制ＣＮＥ—２Ｚ细胞生长的结果,提示这些癌基因可能参与了ＰＫＣ对ＣＮＥ—２Ｚ细胞生长的调节。     

酪氨酸蛋白激酶和蛋白激酶C对N-乙酰氨基葡萄糖转移酶V的双重调控

在人肝癌细胞７７２１中研究了酪氨酸蛋白激酶（ＴＰＫ）和蛋白激酶Ｃ（ＰＫＣ）的激活剂［分别为表皮生长因子（ＥＧＦ）和佛波酯（ＰＭＡ）］和各种蛋白激酶抑制剂对Ｎ－乙酰氨基葡萄糖转移酶Ｖ（ＧｎＴ－Ｖ）活力的影响,以探讨ＴＰＫ和ＰＫＣ对ＧｎＴ－Ｖ的调节。结果发现,ＥＧＦ或ＰＭＡ处理细胞４８ｈ后,ＧｎＴ－Ｖ的活力明显增高;蛋白激酶的非特异性抑制剂槲皮素和染料木黄酮（ｇｅｎｉｓｔｅｉｎ）在抑制ＴＰＫ和ＰＫＣ的同时,抑制ＧｎＴ－Ｖ的基础活力,并完全阻断ＥＧＦ或ＰＭＡ对ＧｎＴ－Ｖ的增高作用;ＴＰＫ的特异性抑制剂Ｔｙｒｐｈｏｓｔｉｎ－２５和ＰＫＣ的特异性抑制剂Ｄ－鞘氨醇分别应用时,各自只能部分地取消ＥＧＦ或ＰＭＡ对ＧｎＴ－Ｖ的诱导。但当Ｔｙｒｐｈｏｓｔｉｎ－２５和Ｄ－鞘氨醇同时加入培养基中则可完全阻断ＥＧＦ或ＰＭＡ对ＧｎＴ－Ｖ的诱导激活。蛋白质合成抑制剂环己亚胺和蛋白激酶抑制剂作用相仿,不但可抑制ＧｎＴ－Ｖ的基础活力,也可完全消除ＥＧＦ或ＰＭＡ对ＧｎＴ－Ｖ的激活。以上结果提示ＥＧＦ或ＰＭＡ通过蛋白激酶调节ＧｎＴ－Ｖ的酶蛋白合成,并且ＧｎＴ－Ｖ受到膜性ＴＰＫ和ＰＫＣ的双重调节,其中ｍ－ＴＰＫ较ｍ－ＰＫＣ更为重要。     

丝裂素活化蛋白激酶参与内皮素刺激的兔主动脉平滑肌细胞增生

内皮素（ｅｎｄｏｔｈｅｌｉｎ,ＥＴ）是已知的体内活性最强的缩血管物质,其缩血管作用由Ｇ蛋白偶联受体所介导。但ＥＴ强大的促血管平滑肌细胞（ＶＳＭＣ）增生效应的机理尚未完全阐明。本研究选用培养的兔胸主动脉ＶＳＭＣ,探讨丝裂素活化蛋白激酶（ＭＡＰＫ）在ＥＴ促细胞增生中的作用。结果表明：ＥＴ－１呈时间和浓度依赖性地促进细胞摄取￣３Ｈ－ＴｄＲ和激活ＭＡＰＫ,此作用可被蛋白激酶Ｃ（ｐｒｏｔｅｉｎｋｉｎａｓｅＣ,ＰＫＣ）抑制剂Ｓｔａｕｒｏｓｐｏｒｉｎｅ（ＳＴＰ）,Ｈ－７和ＥＴ＿Ａ受体拮抗剂ＢＱ１２３所抑制,但不被酪氨酸激酶抑制剂ＨｅｒｂｉｍｙｃｉｎＡ（Ｈｅｒｂ）所抑制,用ＰＫＣ激动剂ＰＭＡ（Ｐｈｏｒｂｏｌｍｙｒｉｓｔａｔｅａｃｅｔａｔｅ）预处理ＶＳＭＣ,使其ＰＫＣ活性下调,可显著减弱ＥＴ－１对ＭＡＰＫ的激活能力。本结果提示：（１）ＭＡＰＫ参与ＥＴ－１所致的ＶＳＭＣ增生;（２）ＥＴ－１促细胞增生与激活ＭＡＰＫ的作用是由ＥＴ＿Ａ受体和ＰＫＣ介导的。     

Translocation of protein kinase C is not required to inhibit the antigen-induced increase of cytosolic calcium in a mast cell line

Cross-linking of receptor bound IgE antibodies by multivalent antigen (DNP8-BSA) on PB-3c cells leads to an increase of cytosolic calcium ((Ca2+)i). Active tumor promoting phorbol esters and teleocidin which specifically activate the phospholipid Ca2+-sensitive protein kinase (PKC), inhibited the antigen-mediated rise in (Ca2+)i and induced a time and dose-dependent translocation of cytosolic PKC to membranes of the PB-3c cells as determined by enzyme activity or immunoblotting using a polyclonal anti-PKC antibody. This TPA concentration did not affect the subcellular distribution of PKC, although 1 nM of 12-O-tetradecanoylphorbol-13-acetate (TPA) inhibited to 50% the antigen-mediated increase in (Ca2+)i. The concentration of TPA required to induce a half-maximal subcellular redistribution of immunodetectable PKC activity was an order of magnitude greater than the half-maximal dose required to inhibit the antigen-mediated increase in (Ca2+)i. These data demonstrate that the TPA-dependent activation of PKC is not directly coupled to its translocation to membranes.     

Cytosolic and Nuclear Mitogen-Activated Protein Kinases Are Regulated by Distinct Mechanisms

We have investigated the regulation and localization of mitogen-activated protein kinase (MAPK) and mitogen-activated protein kinase kinase (MAPKK) in both cytosolic and nuclear fractions of glomerular mesangial cells. p42 MAPK was localized by both immunoblot and kinase activity in both cytosol and nucleus and was rapidly activated, in both fractions, by fetal bovine serum and TPA. Downregulation of protein kinase C (PKC) by TPA inhibited stimulation of cytosolic p42 MAPK, but unexpectedly had no effect on stimulated p42 MAPK in the nucleus. Next we studied the upstream kinase p45 MAPKK by indirect immunofluorescence microscopy, Western blot analysis, and kinase specific activity. Unlike MAPK, p45 MAPKK is almost exclusively cytosolic in resting cells and kinase activity stimulated by TPA is restricted to the cytosol. Interestingly, PKC downregulation for 24 h with TPA dramatically enhanced nuclear MAPKK as assessed by all three techniques. Cytosolic stimulated MAPKK was attenuated in PKC downregulation. Collectively these results show that in mesangial cells: (i) p42 MAPK and p45 MAPKK localize in both the cytosol and the nucleus, and (ii) PKC exerts a negative effect on nuclear MAPKK activity as documented by PKC downregulation, which augments p45 MAPKK nuclear mass and activity. These results indicate that the dual regulation of these two kinases is under differential control in the cytosol and the nucleus.     

慢性缺氧大鼠肺动脉一氧化氮合酶与蛋白激酶C表达变化关系的免疫组织化学研究

观察慢性缺氧对大鼠肺动脉诱导型一氧化氮合酶 (i NOS)和蛋白激酶 C (PKC)表达的影响 ,并探讨 i NOS及 PKC的相互关系在肺动脉高压形成中的作用。建立常压缺氧肺动脉高压模型。应用免疫组化染色和计算机定量图像分析技术观察各组 i NOS和 PKC在蛋白质水平表达的变化 ,并分析二者之间的关系。结果表明随着缺氧时间的延长 ,PKC的表达逐渐上升而 i NOS的表达逐渐下降 ,直线相关分析结果呈显著性负相关 (n=2 4,r=- 0 .94,P<0 .0 1) ,提示 i NOS与 PKC相互拮抗作用与缺氧性肺动脉高压的形成及发展有关     

SUBCELLULAR DISTRIBUTION OF A HEAT-STABLE PROTEIN INHIBITOR OF CYCLIC AMP-DEPENDENT PROTEIN KINASE IN RAT BRAIN

Abstract— Cyclic AMP (cAMP)-dependent protein kinase catalyzes the phosphorylation of polypeptidic serine and threonine residues according to the following chemical equation: ATP + protein → phospho-protein + ADP. A heat stable, trypsin labile factor present in brain, skeletal muscle and other tissues inhibits enzymatic phosphorylation of some proteins and enhances that of others. Since brain is one of the richest sources of adenylate cyclase, cAMP, cAMP-dependent protein kinase and the heat stable protein kinase inhibitor and because they may play a role in neurotransmission, an investigation of the subcellular distribution of the heat stable factor in rat brain was undertaken. Although present in the nuclear, mitochondrial and microsomal fractions, the highest activity of protein kinase inhibitor is in the soluble fraction: its activity parallels that of the cytoplasmic enzyme marker, lactate dehydro-genase. The inhibitory activity is also found in the synaptosome or pinched-off nerve ending fraction. Following osmotic lysis of this fraction, about 90% of the factor occurs in the soluble fraction. On the other hand, only 40% of the cAMP-dependent protein kinase is solubilized and 60% remains membrane-bound. Using this membrane-bound protein kinase, phosphorylation of endogenous substrate is unaltered by inhibitor, but phosphorylation of added histone substrate is decreased.     

Inhibition of protein kinase C by ether-linked lipids is not correlated with their antineoplastic activity on WEHI-3B and R6X-B15 cells.

To test the hypothesis that the action of antineoplastic ether-linked lipids in leukemic cells is associated with their ability to inhibit protein kinase C (PKC), we have compared the effects of two ether-linked lipids, 1-O-hexadecyl-2-O-methyl-sn-glycero-3-phosphocholine (ET16-OCH3-GPC) and 1-O-hexadecyl-2-O-methyl-sn-glycero-3-(S-beta-D-1'- thioglucopyranosyl)-sn-glycerol (ET16-OCH3-beta-thio-Glc), on two different leukemic cell lines (WEHI-3B and R6X-B15). ET16-OCH3-GPC killed WEHI-3B cells with an EC50 value of 2.5 microM, whereas it was far less effective against R6X-B15 cells (EC50 = 40 microM). In contrast, the beta anomer of ET16-OCH3-beta-thio-Glc did not kill either cell line at concentrations up to 40 microM. Both ET16-OCH3-GPC and ET16-OCH3-thio-Glc inhibited 12-O-tetradecanoylphorbol 12,13-dibutyrate (TPA)-induced PKC translocation in both WEHI-3B and R6X-B15 cells. When WEHI-3B cells were first exposed to TPA, and then to ET16-OCH3-GPC, no significant decrease in PKC activity in the particulate fraction was noticed. When, however, the cells were first exposed to ET16-OCH3-GPC and then to TPA, the enzyme activity in the particulate fraction was decreased by 20-30%. A phorbol dibutyrate binding assay showed that the decrease in membrane-associated PKC activity and the increase in cytosolic PKC activity did not result from impeded enzyme translocation. These results suggest that the similar PKC inhibitory potency of ET16-OCH3-GPC and ET16-OCH3-beta-thio-Glc: (a) is not correlated with the widely different cytotoxicities of these agents and (b) is probably due to interference with the binding of diacylglycerol/phosphatidylserine or TPA to PKC. Taken together, these results suggest that the ether-linked lipids compete with diacylglycerol/phosphatidylserine or TPA for binding sites on PKC required for enzyme activation.     

Levels of protein kinase C activity in human gastrointestinal cancers

The protein kinase C (PKC) activities of tumor tissue and adjacent normal mucosa of human cancers of the esophagus (8 cases), stomach (1 case) and colon (3 cases) were measured. Considerable variations were found in the activity of PKC and in its subcellular distribution in these cancers. The PKC activities of the membrane and cytosolic fractions of the eight esophageal cancers were, however, similar to those of the adjacent normal mucosa: the average PKC activities of the tumor tissues and normal mucosa were 7.5 and 8.3 pmol/min/mg protein, respectively, in their membrane fractions and 7.9 and 7.8 pmol/min/mg protein, respectively, in their cytosolic fractions.     

蛋白激酶C参与缺氧预处理的血管平滑肌细胞保护

已知缺氧预处理不仅对心肌细胞,而且对血管床亦有保护作用;但对血管壁细胞是否有直接保护作用,目前尚不清楚。本工作在培养的家兔血管平滑肌细胞（ＶＳＭＣ）缺氧复氧（Ａ／Ｒ）损伤模型上观察缺氧预处理（ａｎｏｘｉｃｐｒｅｃｏｎｄｉｔｉｏｎｉｎｇ,ＡＰＣ）的影响。发现ＡＰＣ能提高Ａ／Ｒ后ＶＳＭＣ存活率,减轻细胞脂质过氧化损伤和钙超载,使用蛋白激酶Ｃ（ＰＫＣ）激动剂ＰＭＡ能模拟,而抑制剂Ｈ７或ｐｏｌｙｍｙｘｉｎＢ能完全消除ＡＰＣ的上述保护作用。提示ＡＰＣ对ＶＳＭＣ的Ａ／Ｒ损伤具有保护作用,其机理可能与ＰＫＣ激活有关