Temporal dissociation of frequency-dependent acceleration of relaxation and protein phosphorylation by CaMKII

Frequency-dependent acceleration of relaxation (FDAR) is an important intrinsic mechanism that allows for diastolic filling of the ventricle at higher heart rates, yet its molecular mechanism is still not understood. Previous studies showed that FDAR is dependent on functional sarcoplasmic reticulum (SR) and can be abolished by phosphatase or by Ca/CaM kinase (CaMKII) inhibition. Additionally, CaMKII activity/autophosphorylation has been shown to be frequency-dependent. Thus, we tested the hypothesis that CaMKII phosphorylation of SR Ca(2+)-handling proteins (Phospholamban (PLB), Ca(2+) release channel (RyR)) mediates FDAR. Here we show that FDAR occurs abruptly in fluo-4 loaded isolated rat ventricular myocytes when frequency is raised from 0.1 to 2 Hz. The effect is essentially complete within four beats (2 s) with the tau of [Ca(2+)](i) decline decreasing by 42+/-3%. While there is a detectable increase in PLB Thr-17 and RyR Ser-2814 phosphorylation, the increase is quantitatively small (PLB<5%, RyR approximately 8%) and the time-course is clearly delayed with regard to FDAR. The low substrate phosphorylation indicates that pacing of myocytes only mildly activates CaMKII and consistent with this CaMKIIdelta autophosphorylation did not increase with pacing alone. However, in the presence of phosphatase 1 inhibition pacing triggered a net-increase in autophosphorylated CaMKII and also greatly enhanced PLB and RyR phosphorylation. We conclude that FDAR does not rely on phosphorylation of PLB or RyR. Even though CaMKII does become activated when myocytes are paced, phosphatases immediately antagonize CaMKII action, limit substrate phosphorylation and also prevent sustained CaMKII autophosphorylation (thereby suppressing global CaMKII effects).     

Potential role of protein kinase C on the differentiation of erythroid progenitor cells

The effect of protein kinase C inhibitors, staurosporine and 1-(5-isoquinolinyl sulfonyl)-2-methyl piperazine(H7) onin vitro differentiation of erythroid progenitor cells which were isolated from spleens of mice infected with the anemia-inducing strain of Friend virus were examined. Erythropoietin-mediated differentiation of erythroid progenitor cells, as determined by the incorporation of⁵⁹Fe into protoporphyrin, was inhibited by staurosporine and H7 in a concentration-dependent manner. Scatchard analysis of the³H-phorbol-12, 13-dibutyrate binding to erythroid progenitor cells revealed that at the high affinity sites the dissociation constant was 22nM and the maximum number of³H-phorbol-12,13-dibutyrate binding sites per cell was approximately 3.7×10⁵. Cytosolic protein kinase C was isolated from erythroid progenitor cells and then purified by sequential column chromatography. Two isoforms of protein kinase C were found. Photoaffinity labeling of the purified protein kinase C samples with³H-phorbol 12-myristate 13-acetate followed by analysis of SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and autofluorography showed radiolabeled 82-KDa peptides. Radiolabeling of the 82-kDa peptides with³H-phorbol 12-myristate 13-acetate was almost completely blocked by excess unlabeled phorbol 12-myristate 13-acetate. Results of phorbol 12-myristate 13-acetate-promoted phosphorylation with the purified protein kinase C samples showed that the phosphorylation of 82-kDa peptides was increased as the concentration of phorbol 12-myristate 13-acetate was increased from 10⁻⁸ M to 10⁻⁴M. In light of the findings that erythroid progenitor cells possessed an abundance of protein kinase C and that staurosporine and H7 inhibited erythroid differentiation, it seemed likely that protein kinase C would play a role in the erythroid progenitor cell development.     

A Murine Monoclonal Antibody that Recognizes an Extracellular Domain of the Human c-erbB-2 Protooncogene Product

A marine IgM monoclonal antibody, designated SV2–61, was generated against human c-erbB-2 gene-transfected NIH-3T3 (SV11) cells. SV2–61 defined a 185-kDa molecule present on the surface of SV11 cells, another line of c-erbB-2 gene-transfected NIH-3T3 (A4–15) cells, and MKN-7 human gastric cancer cell line carrying an amplified human c-erbB-2 gene. The SV2–61-defined antigen was found to show protein kinase activity in vitro . The SV2–61 was reactive with human c-erbB-2 gene-transfected NIH-3T3 cell lines but not with transfectants carrying c-erbB-2 gene mutants which lack a coding region for the extracellular domain. It was reactive with a portion of human epithelial cell lines hut not with native NIH-3T3, TGF-a-coding gene-, activated c-raf gene- or Ha-ras gene-transfected NIH-3T3 cells, or non-epithelial human cells. These results indicate that the SV2–61 is an antibody which recognizes an extracellular domain of the c-erbB-2 gene product, 185-kDa protein.     

Presence of Bacterial 16S Ribosomal RNA Gene Segments in Human Intestinal Lymph Follicles

Background: There is currently no information regarding microbial agents inside the intestinal lymph follicles. Methods: Biopsy or resected specimens, mostly from macroscopically normal areas, were sectioned with a cryostat. DNA was extracted from microdissected samples, exclusively from the lymph follicle. Amplification of DNA was performed using universal primers designed from conserved regions of bacterial 16S ribosomal RNA (rRNA). Several clones with inserts of around 400 base pairs were subjected to DNA sequence analysis followed by a database homology search. Results: Bacterial 16S rRNA gene segments were detected in the lymph follicle in 2 of 14 (14%) non-inflammatory bowel disease (IBD) cases, 4 of 14 (28%) Crohn disease cases, and in 2 of 5 (40%) ulcerative colitis cases. Nineteen 16S rRNA gene segments were recognized in the eight positive cases. Five segments showed 100% identity to known bacterial 16S rRNAs, namely staphylococcus species, Streptococcus sanguis, and Paracoccus marcusii. However, the other 14 segments showed below 100% identity, indicating either the presence of unknown bacteria or of bacteria without known DNA data. No single identified or unidentified bacterium, characteristic of IBD, including Mycobacterium paratuberculosis and Listeria monocytogenes, was detected. Conclusions: The present study confirms the presence of bacterial 16S rRNA gene segments in human intestinal lymph follicles and paves the way for new investigations into the microbiology of the lymph follicle. Whether or not bacteria inside the lymph follicle is a primary stimulus in IBD has yet to be clarified.     

αCaMKII autophosphorylation controls exploratory activity to threatening novel stimuli

Autophosphorylation of αCaMKII is regarded as a ‘molecular memory’ for Ca²⁺ transients and a crucial mechanism in aversely, but less so in appetitively, motivated learning and memory. While there is a growing body of research implicating αCaMKII in general in behavioral responses to threat or fearful stimuli, little is known about the contribution of the autophosphorylation. The present study asked how αCaMKII autophosphorylation controls anxiety-like behavioral responses toward novel, potentially threatening stimuli. We tested homozygous and heterozygous T286A αCaMKII autophosphorylation deficient mice and wild types in a systematic series of behavioral tests. Homozygous mutants were more active in the open field test and showed reduced anxiety-related behavior in the light/dark test, but these findings were confounded by a hyperlocomotor phenotype. The analysis of elevated plus maze showed significantly reduced anxiety-related behavior in the αCaMKII autophosphorylation-deficient mice which appeared to mediate a hyperlocomotor response. An analysis of home cage behavior, where neither novel nor threatening stimuli were present, showed no differences in locomotor activity between genotypes. Increased locomotion was not observed in the novel object exploration test in the αCaMKII autophosphorylation-deficient mice, implying that hyperactivity does not occur in response to discrete novel stimuli. The present data suggest that the behavior of αCaMKII autophosphorylation-deficient mice cannot simply be described as a low anxiety phenotype. Instead it is suggested that αCaMKII autophosphorylation influences locomotor reactivity to novel environments that are potentially, but not necessarily threatening.     

The tyrphostin B42 inhibits cell proliferation and HER-2 autophosphorylation in cervical carcinoma cell lines

The HER family receptors have an important role controlling cell growth and differentiation. Although the activity of the HER-2 receptor is strictly controlled in normal cells, its overexpression plays a pivotal role in transformation and tumorigenesis. Constitutive phosphorylation of HER-2 protein has been implicated in conferring uncontrolled growth to mammary cancer cells, and to a lesser extent, with adenocarcinoma of uterus, cervix, fallopian tube, and endometrium. This study addresses the role of HER-2 in cervical carcinoma. Firstly, we demonstrate the presence of HER-2 protein expression by flow cytometry in two new cervical carcinoma cell lines CALO and INBL. Secondly, we use the specific tyrosine kinase inhibitors, Tyrphostins to examine HER-2 regulation by the crystal violet assay. Thirdly, we use western blot analysis to assess the state of HER-2 phosphorylation. The most efficient agent, Tyrphostin B42, known as an inhibitor of epithelial growth factor receptor, arrested cervical carcinoma cell lines growth in vitro at micromolar concentrations within 72 h of application. Tyrphostin B42 inhibited the HER2 signal-regulated kinase pathway, as observed by the reduction in the phosphorylated forms of HER2. The loss of phosphorylated forms of HER2 at early time points after Tyrphostin B42 application was associated with suppression of cell growth. Thus, the inhibition of the proliferation of our cervical carcinoma cell lines by Tyrphostin B42 is associated with inhibition of HER2 protein kinase signal.     

人红细胞胰岛素受体自身磷酸化的酶联免疫吸附测定

目的建立人红细胞胰岛素受体自身磷酸化测定法。方法应用合成的磷酸酪氨酸钥孔帽贝血蓝蛋白（ＰＹＫＬＨ）免疫家兔得到抗血清，将纯化的抗磷酸酪氨酸抗体作为第一抗体，羊抗兔Ｉｇ酶结合物（辣根过氧化物酶标记）作为第二抗体，建立双抗体夹心酶联免疫吸附测定法。结果批内变异系数为８．４％，批间变异系数为９．０％。２０例健康人的红细胞ＩＲ的自身磷酸化活性，测定值为０．１５０±０．０２２ｎｍｏｌＰＹ／ｍｇ受体蛋白。在体外，胰岛素在１０－６ｍｏｌ／Ｌ时对自身磷酸化达到最大激活。结论用酶免法测定人红细胞胰岛素受体灵敏、特异、简便，为胰岛素作用机制的理论研究、胰岛素受体基因突变的检测和糖尿病及其它胰岛素抵抗综合症的病因及治疗的探讨提供了有效的方法。     

The insulin resistant subphenotype of polycystic ovary syndrome: clinical parameters and pathogenesis

Objective

This study was undertaken to compare clinical and biochemical characteristics of the insulin resistant (IR) and non-IR subphenotypes of polycystic ovary syndrome (PCOS).

Study design

Infertile PCOS women were classified as IR (n = 32) or non-IR (n = 46) on the basis of fasting glucose and insulin levels. The incidence of acanthosis nigricans (AN), hirsutism, and ovulation in response to clomiphene citrate (CC) was compared between the 2 groups, along with serum levels of gonadotropins, and sex steroids. Blood samples from 28 PCOS patients and 8 controls were analyzed by enzymatic immunoassay for autophosphorylated insulin receptor (APIR) and total insulin receptor (TIR) content.

Results

Insulin resistance was associated with obesity (odds ratio [OR] = 3.5, P < .05), AN (OR = 6.0, P < .05), hirsutism (OR = 3.1, P < .05), and resistance to CC (OR = 5.0, P < .05). Mean levels of LH, LH/FSH ratios, and testosterone were lower in women with IR (11.5 ± 6.8 mIU/mL, 2.0 ± 1.0, and 56.6 ± 29.0 ng/dL, respectively) compared with women without IR (15.0 ± 13.4 mIU/mL, 2.4 ± 1.5, and 72.5 ± 29.8 ng/dL, respectively) (P < .05). Mean APIR/TIR ratios in IR women were lower than in non-IR women (P < .05 at 100 nmol/L of insulin) and controls (P < .01 at 1, 10 and 100 nmol/L insulin).

Conclusion

Patients with IR are more likely to be obese and have AN, hirsutism, resistance to CC, and lower LH, LH/FSH ratios, and testosterone levels. Furthermore, IR patients appear to have defective autophosphorylation of the insulin receptor, a key element in insulin action, and a possible mechanism for IR in PCOS.     

Inhibition of insulin-like growth factor I receptor autophosphorylation by novel 6-5 ring-fused compounds

The insulin-like growth factor 1 receptor (IGF1R) plays an important role in cell transformation, and it has emerged as a target for anti-cancer drug design. IGF1R is activated by autophosphorylation at three sites in the enzyme activation loop. We describe here a group of 6-5 ring-fused compounds that are the first reported inhibitors selective for the unphosphorylated (0P) form of IGF1R. These compounds do not significantly inhibit the fully activated, triply phosphorylated (3P) form. IGF1R was produced from baculovirus-infected Spodoptera frugiperda (Sf9) cells, and the 0P and 3P forms were purified to homogeneity. We used a continuous spectrophotometric assay to measure inhibition of the 0P and 3P forms. Analysis by native gel electrophoresis confirmed that the step inhibited in the autoactivation process was the transition between the 0P and IP forms of IGF1R. The compounds were also active against IGF1R autophosphorylation in intact Chinese hamster ovary (CHO) cells. Most of the compounds also inhibited the closely related insulin receptor to varying degrees, although some compounds showed selectivity for IGF1R or insulin receptor. This class of compounds could form the basis of design efforts to selectively block the autoinhibited conformation of IGF1R.     

Ca-independent activity of Ca/calmodulin-dependent protein kinase II involved in stimulation of neurite outgrowth in neuroblastoma cells

We investigated the involvement of Ca²⁺-independent activity of Ca²⁺/calmodulin-dependent protein kinase II (CaM kinase II) in stimulation of neurite outgrowth. When neuroblastoma Neruo2a (Nb2a) cells expressing the α isoform of CaM kinase II (Nb2a/α cells) were stimulated by plating, they changed shape from round to flattened, and began to form neurites within 15 min. Numbers of cells bearing neurites increased from 15 min to about 2 h. Neurite length increased markedly from 30 min to 2 h after stimulation. Ca²⁺-independent activity of CaM kinase II increased immediately after stimulation, peaked at about 30 min, and then gradually decreased. Autophosphorylation of Thr-286 followed the same time course as the increase in Ca²⁺-independent activity. The autophosphorylation and appearance of Ca²⁺-independent activity preceded the formation of neurites. The effect of mutation of the autophosphorylation site in the kinase whose Thr-286 was replaced with Ala (αT286A kinase) or Asp (αT286D kinase) was examined. αT286A kinase was not converted to a Ca²⁺-independent form, and αT286D kinase had Ca²⁺-independent activity significantly as an autophosphorylated kinase. Cells expressing αT286A kinase did not form neurites, and were indistinguishable from control Nb2a cells. Cells expressing αT286D kinase had much longer neurites than Nb2a/α cells expressing the wild type kinase, although the initiation of neurite outgrowth was very late. These results indicated that Ca²⁺-independent activity of the kinase autophosphorylated at Thr-286 involves for neurite outgrowth.