The aging brain, a key target for the future: The protein kinase C involvement

The brain represents the primary centre for the regulation and control of all our body activities, receiving and interpreting sensory impulses and transmitting information to the periphery. Most importantly, it is also the seat of consciousness, thought, emotion and especially memory, being in fact able to encode, store and recall any information. Memory is really what makes possible so many of our complex cognitive functions, including communication and learning, and surely without memory, life would lose all of its glamour and purpose. Age-associated mental impairment can range in severity from forgetfulness at the border with pathology to dementia, such as in Alzheimer's disease. In recent years, one of the most relevant observations of research on brain aging relates to data indicating that age-related cognitive decline is not only due to neuronal loss, as previously thought; instead, scientists now believe that age-associated functional changes have more to do with the dysfunctions occurring over time. Within this context a prominent role is certainly played by signal transduction cascades which guarantee neuronal cell to elaborate coordinated responses to the multiple signals coming from the outside and to adapt itself to the environmental changes and requests. This review will focus the attention on protein kinase C pathway, with a particular interest on its activation process, and on the role of protein-lipid and protein-protein interactions to selectively localize the cellular responses. Furthermore, information is emerging and will be discussed on the possibility of mRNA stabilization through PKC activation. This review will also approach the issue on how alterations of these molecular cascades may have implications in physiological and pathological brain aging, such as Alzheimer's disease.     

RACK1在苯环利定致精神分裂症模型小鼠脑中的分布特点

目的:建立苯环利定(Phencyclidine,PCP)诱导精神分裂症小鼠模型,考察活化的蛋白激酶C受体1(Receptor for activated C kinase 1,RACK1)在脑内的表达变化。方法:将48只雄性C57BL/6小鼠随机分为对照组和精神分裂症模型组(n=24)。模型组小鼠皮下注射PCP1.5 mg?kg^-1,对照组皮下注射等体积生理盐水,连续注射7d后进行刻板行为实验,记录刻板行为评分,并采用免疫荧光染色测定全脑RACK1的表达情况。结果:与对照组相比,PCP皮下注射导致小鼠反复摇头、转圈等刻板行为明显增加(P<0.05),且小鼠脑内小胶质细胞明显增生活化。免疫荧光检测结果显示,PCP小鼠海马RACK1表达明显增强,主要表达于神经元,未见与小胶质细胞的共定位。结论:精神分裂症小鼠的刻板行为可能与海马神经元RACK1高表达相关。     

Molecular cloning and characterization of a receptor for activated protein kinase C1 (RACK1) from Chinese white shrimp; Fenneropenaeus chinensis

Receptor for activated C kinase 1 (RACK1), which has seven tandem WD40 domains, is a scaffolding protein. RACK1 plays different roles by binding to different partner proteins. It is involved in hormone signaling and development, and now some evidence indicates it may have a role in innate immunity. In this paper, RACK1 cDNA from Chinese white shrimp (FcRACK1) was identified. The full length of the FcRACK1 gene is 1037 bp, including a 30 bp 5′UTR, a 957 bp ORF encoding a 318 amino acid protein, and a 50 bp 3′UTR with the polyadenylation sequence AATAAA and a poly (A) tail. The FcRACK1 protein is characterized by seven WD40 repeat domains; the ending two amino acids of each WD40 domain are WK, WD, WN, WS, WD, WD, and WQ, respectively. The length of each domain is between 30 and 44 amino acids. Multiple alignments of RACK1s showed that RACK1s are highly conserved. RT-PCR showed that FcRACK1 could be detected in hemocytes, the heart, hepatopancreas, gills, stomach, intestine, and ovary. FcRACK1 in hemocytes was down-regulated after a 2 h WSSV challenge, and FcRACK1 in gills was up-regulated after a 2 h Vibrio challenge. FcRACK1 in ovary went down after a 12 h Vibrio challenge and then up-regulated at 24 h. FcRACK1 in ovary was first down-regulated at 2 h after a WSSV challenge and then up-regulated to the highest level at 6 h. It finally went down from 12 to 24 h. In hepatopancreas, FcRACK1 was also up-regulated by microbe challenge. Our results indicated its probable role in shrimp innate immunity.     

Inflammation and inflammatory agents activate protein kinase C epsilon translocation and excite guinea-pig submucosal neurons

BACKGROUND & AIMS: Properties of enteric neurons are transformed by inflammation and protein kinase C (PKC) isoforms are involved both in long-term changes in enteric neurons, and in transducing the effects of substances released during inflammation. We investigated roles of PKCepsilon in submucosal neurons by studying translocation in response to inflammatory mediators, effects on neuron excitability, and the changes in PKCepsilon distribution in a trinitrobenzene sulphonate model of ileitis. METHODS: Immunohistochemical detection and analysis of association with membrane and cytosolic fractions, and Western blot analysis of cytosolic and particulate fractions were used to quantify translocation. Electrophysiology methods were used to measure effects on neuron excitability. RESULTS: All submucosal neurons were immunoreactive for the novel PKC, PKCepsilon, and direct PKC activators, phorbol 12,13-dibutyrate, ingenol 3,20-dibenzoate, and the PKCepsilon-specific activator, transactivator of transduction-Psiepsilon receptor for activated C kinase, all caused PKCepsilon translocation from cytoplasm to surfaces of the neurons. Electrophysiologic studies showed that the stimulant of novel PKCs, ingenol (1 micromol/L), increased excitability of all neurons. Stimulation of protease-activated receptors caused PKCepsilon translocation selectively in vasoactive intestinal peptide secretomotor neurons, whereas a neurokinin 3 tachykinin receptor agonist caused translocation in neuropeptide Y and calretinin neurons. In all cases translocation was reduced significantly by a PKCepsilon-specific translocation inhibitor peptide. Increased PKCepsilon at the plasma membrane occurred in all neurons 6-7 days after an inflammatory stimulus. CONCLUSIONS: Major targets for PKCepsilon include ion channels near the plasma membrane. PKCepsilon is likely to have a significant role in controlling the excitability of submucosal neurons and is probably an intermediate in causing hyperexcitability after inflammation.     

hPeriod1PAS结构域相互作用蛋白的筛选和研究

目的寻找与近日节律系统核心基因Period1（Per1）相互作用的新蛋白，揭示近日节律相关的可能信号通路。方法采用酵母双杂交方法，以人Per1的PAS结构域为诱饵，扫描人下丘脑cDNA文库，并通过体外转录、免疫共沉淀验证蛋白间相互作用；通过RT—PCR检测RACK1（receptors for activated Ckinase）表达的组织特异性及节律性；运用RNAi技术初步研究RACK1与Per1的信号联系。结果人下丘脑区域RACK1蛋白与Per1存在相互作用；RACK1在多器官组织保守表达，但其表达未呈现明显节律性；上调及下调Per1表达，RACK1的RNA水平无显著变化。结论细胞内接头分子RACK1是一种新的Per1作用蛋白，可能介导、调控Per1的功能。     

Interaction of Gbetagamma with RACK1 and other WD40 repeat proteins

Heterotrimeric G-proteins, composed of Galpha and Gbetagamma subunits, transmit numerous and diverse extracellular stimuli via a large family of heptahelical cell-surface receptors to various intracellular effector molecules. The Gbetagamma subunit plays a central role in G-protein signaling. The Gbeta subunit belongs to a large family of WD40 repeat proteins, which adopt a circular beta-bladed propeller structure. This unique structural feature confers interactions of Gbetagamma with a variety of proteins to play diverse functions. Intriguingly, we recently found that Gbetagamma can interact with three other WD40 repeat proteins, receptor for activated C kinase 1 (RACK1), dynein intermediate chain-1A and a protein of unknown function. This raises the following questions: are interactions among WD40 proteins a common theme and does the formation of a WD40-WD40 repeat protein complex constitute a protein scaffold for integrating signals from different cellular processes. We are beginning to address these issues by studying the interaction between Gbetagamma and RACK1. Here we will describe the molecular mechanism underlying this interaction and the implications of the interaction on the signal transduction of G-protein and RACK1.     

慢性吗啡成瘾小鼠海马中RACK1对CREB表达水平的影响

目的：研究shRAKC1对慢性成瘾小鼠脑组织CREB mRNA、蛋白的表达变化。方法：通过条件性位置偏爱（CPP）实验分析shRAKC1对慢性吗啡成瘾小鼠的作用;通过RT-PCR检测RACK1和CREB的mRNA在成瘾小鼠海马中的表达水平,并采用免疫组化观察RACK1和CREB蛋白的表达情况。结果：慢性成瘾组与生盐水组相比,前者海马区RACK1和CREBmRNA表达升高（p〈0．05）,且吗啡诱导的CPP效应增强（p〈0．05）,而shRAKC1组与空质粒组相比,前者由吗啡诱导的CPP诱导效应减弱（p〈0．05）,同时其海马区RACK1和CREBmRNA表达下降（p〈0．05）。结论：干扰慢性吗啡成瘾小鼠RACK1表达,可以使CREB表达水平下调,并有抑锏吗啡成瘾效应的作用。     

RACK1: A superior independent predictor for poor clinical outcome in breast cancer

We aimed to investigate the expression of RACK1 in breast cancer, evaluate its role in predicting prognosis and compare with commonly used biomarkers: Ki67, ER, PR and HER‐2 for patients with breast cancer. The RACK1 expression and its clinical significance were examined in 160 breast carcinoma patients using immunohistochemistry. Correlations of RACK1 expression with other commonly used biomarkers and survival analyses were assessed. Immunohistochemistry results showed that the number of RACK1 cases scoring 0, 1, and 2 were 66, 54, and 40, respectively. RACK1 staining was strongly related to clinical stage, histological grade, Ki67, ER, PR and HER‐2 (all p < 0.05). Consistently, all of the cases exhibiting RACK1 staining score 0 were survivors, whereas the majority (55.0%) of those exhibiting RACK1 staining score 2 were deaths. Kaplan‐Meier survival analysis of 160 cases revealed a correlation between higher RACK1 expression levels and shorter overall survival times (p < 0.001). Univariate and multivariate analyses revealed that RACK1, tumor size, lymph node metastasis, and HER‐2 were independent prognostic factors (all p < 0.05). Interestingly, receiver operator characteristic (ROC) curves showed that the ROC areas for RACK1, Ki67, ER, PR and HER‐2 were 0.833, 0.766, 0.446, 0.387, and 0.689, respectively, and the superiority of RACK1 in sensitivity and specificity as biomarker was demonstrated. To our knowledge, it is the first time to investigate the expression of RACK1, and identified that RACK1 is a superior independent biomarker for diagnosis and prognosis comparing with currently widely used diagnostic index in breast carcinoma.