Biomedical subjects

K Takeda

Publications and source records attributed to K Takeda.

At least 181 records · Page 10Linked to original sources

PubMed2001

Pharmacological characterization of KUR-1246, a selective uterine relaxant.

The aim of the present study was to evaluate the efficacy and beta 2-adrenoceptor (AR) selectivity of KUR-1246, a new uterine relaxant. Inhibition of spontaneous or drug-induced uterine contractions by KUR-1246 was evaluated in pregnant rats and rabbits by an organ bath method or by a balloon method. The selectivity of KUR-1246 was assessed simultaneously in organs isolated from late-pregnant rats. The affinity of KUR-1246 for human beta 1-, beta 2-, and beta 3-ARs was determined using two radioligands. KUR-1246 suppressed both spontaneous and drug-induced contractions in isolated uteri, the rank order of potency being isoproterenol > KUR-1246 > terbutaline > ritodrine. ICI-118551 (selective beta 2-AR antagonist) competitively antagonized the KUR-1246-induced inhibition of spontaneous uterine contractions, but CGP-20712A (selective beta 1-AR antagonist) and SR-58894A (selective beta 3-AR antagonist) did not. All beta-AR agonists tested produced significant inhibition of spontaneous uterine contractions in vivo: ED(30) value for KUR-1246 was 0.13 microg/kg/min, a potency about 6 times and 400 times greater than that of terbutaline and ritodrine, respectively. In contrast, the positive chronotropic effect was minimal in KUR-1246-treated rats. KUR-1246 displaced radioligand binding to beta 1-, beta 2-, and beta 3-ARs, the pK(i) values being 5.75 +/- 0.03, 7.59 +/- 0.08, and 4.75 +/- 0.03 for beta 1-, beta 2-, and beta 3-ARs, respectively. For the selectivity of KUR-1246 for human beta 2-AR, we obtained values of 39.2 ([IC(50) for beta 1-AR]/[IC(50) for beta 2-AR]) and 198.2 ([IC(50) for beta 3-AR]/[IC(50) for beta 2-AR]), indicating an apparently higher affinity for human beta 2-AR than for other beta-AR subtypes. The present study clearly demonstrated that KUR-1246 is a more selective beta 2-AR agonist than the drugs presently used for relaxing uterine muscle.

Acetamides↗

PubMed2001

Critical contribution of IFN-gamma and NK cells, but not perforin-mediated cytotoxicity, to anti-metastatic effect of alpha-galactosylceramide.

The glycolipid alpha -galactosylceramide (alpha -GalCer), which is presented by CD1d and specifically activates Valpha 14 NKT cells, exerts a potent anti-metastatic effect when administered in vivo. In this study, we demonstrated that alpha -GalCer administration led to rapid elimination of NKT cells by apoptosis in the liver and spleen, after they produced IFN-gamma and IL-4. In contrast, a more prolonged secretion of IFN-gamma was observed by liver and splenic NK cells after alpha -GalCer administration. Cytotoxic activity of liver mononuclear cells was not augmented 3h after alpha -GalCer administration, but was increased at 24 h when NKT cells were mostly depleted. The alpha -GalCer-induced cytotoxic activity was abolished in IFN-gamma -deficient and NK cell-depleted mice as well as CD1-deficient mice, suggesting that the alpha -Galcer-induced cytotoxicity was mainly mediated by IFN-gamma -activated NK cells. While the alpha -GalCer-induced cytotoxicity in vitro was mostly perforin dependent, anti-metastatic effect of alpha -GalCer was impaired in NK cell-depleted or IFN-gamma -deficient mice but not in perforin-deficient mice. Collectively, these results indicated that the anti-metastatic effect of alpha -GalCer is mainly mediated by NK cells, which are activated secondarily by IFN-gamma produced by alpha -GalCer-activated NKT cells, in a perforin-independent manner.

Animals↗

PubMed2001

[Simple method of stereotactic radiotherapy without stereotactic body frame for extracranial tumors].

Thirty-five patients with metastatic lung cancer(46 lesions) and twenty patients with primary lung cancer (21 lesions) have been treated with a simple method of stereotactic radiotherapy (SRT) without stereotactic body frame. Tumor size ranged from 1-4 cm in diameter. We used Vac-Lok cushion(Med-Tek) as a immobilization system. To be sure to include the respiratory movement of tumor to planning target volume(PTV), every patients were examined by fluoroscopy and radio-opaque catheters with the same length of tumor movement were attached on the anterior and lateral chest wall before CT simulation. A gold grain was implanted into a tumor that was invisible on fluoroscopy, as a radiomaker. Protocol of 60 Gy/8 fractions/2 weeks and 45 Gy/3 fractions/3-6 days were mainly used. The median follow-up period was 15 months for primary lung cancer and 19 months for metastatic lung cancer. Local control rates were 91% for metastatic lung cancer, 89% for primary lung cancer and 85% for T1, 2N0M0 cases. All patients developed mild pneumonitis or fibrosis about 4.5 months after SRT just in the treatment volume. Only three patients was symptomatic.

Clinical Trials as Topic↗

PubMed2001

[Transarterial chemoembolization (TAE) with degradable starch microspheres (DSM) in advanced hepatocellular carcinoma].

This study was undertaken to evaluate the clinical utility of chemoembolization using degradable starch microspheres (DSM), which resolve in a short period in patients with advanced hepatocellular carcinoma (HCC). Twenty-one patients underwent DSM chemoembolization 24 times. After a mixture of iodized oil and epirubicin was injected into the hepatic arteries, the patients were embolized with DSM alone 16 times. In the other 8 times, embolization was done in one hepatic lobe with DSM and in the other hepatic lobe with gelatin sponge (GS). There was no major complication related to chemoembolization. Tumor response (complete, partial, and minor responses) was found in 46% of patients after TAE. Tumor recurrence was found in 64% of responders after a mean period of 2.0 months. The response rate was significantly higher when chemoembolization was performed using both DSM and GS than when it was done with DSM alone (63% vs 37%, p < 0.04). Although the response rate after DSM-TAE is low, its anticancer effect is reinforced when used as an adjuvant therapy of GS-TAE.

Aged↗

PubMed2001

[Advanced hepatocellular carcinoma--feasibility and clinical impact of high-dose-rate brachytherapy on the treatment of lesions growing into biliary trees, portal veins and the vena cava].

This study was performed to evaluate the feasibility and clinical impact of intraluminal and endovascular high-dose-rate iridium-192 brachytherapy on the treatment of HCC lesions growing into biliary trees, portal veins and the inferior vena cava. HCCs involving biliary trees in 2 patients, the main and/or first-order portal veins in 3 patients, and the inferior vena cava in 2 patients. Brachytherapy was percutaneously performed with a 5F applicator, which was placed adjacent to the lesions. A mean total dose of 23 Gy (range, 5-7 Gy/fr) was irradiated (at a 5 mm radius) to the biliary or the portal venous tumors. A total dose of 10 Gy (5 Gy/fr) was given to the caval tumors. External-beam radiotherapy was combined in 2 patients with caval lesions, stent placement in 2 patients with biliary lesions and hepatic arterial infusion chemotherapy in 5 patients. There was no major complication except hemobilia, which ceased after placing a PTCD tube in the bile duct in one patient. All tumors were significantly reduced in size and remained controlled during the period of patients' survival. Complete tumor necrosis was histologically proved in 2 autopsy cases having biliary lesions. The median survival was 13 months. Intraluminal and endovascular high-dose-rate brachytherapy appears to be a feasible, and effective procedure to treat advanced HCCs invading biliary trees, portal veins and the vena cava.

Aged↗

PubMed2001

[Hepatic intra-arterial infusion chemotherapy using polymer-coated 2.9 Fr implantable catheter-port system--initial experience].

We developed a new 2.9 Fr implantable catheter-port system (reservoir) to perform arterial infusion chemotherapy in patients with unresectable liver tumors. This study was undertaken to evaluate the feasibility of placing this new reservoir system in patients in whom placement of a 5 Fr-reservoir system would seem to be difficult because of severe stricture, tortuosity or angulation of the hepatic artery. A new reservoir system was successfully implanted in 25 patients during 27 sessions. After a side hole was opened, a 2.9 Fr catheter was inserted in the distal hepatic artery or in the gastroduodenal artery in 24 sessions. The catheter tip was then fixed with coils to prevent catheter dislocation. In the other 3 sessions, a 2.9 Fr catheter was inserted without catheter fixation in the replaced right hepatic artery and a small sized collateral artery towards the liver. Arterial infusion chemotherapy was done without any trouble after 20 sessions. Catheter dislocation was found after 2 sessions in which the catheter tip was not fixed or inadequately fixed. Early arterial occlusion was found after placing a 2.9 Fr catheter in the replaced hepatic artery and the small sized-collateral artery after 4 sessions. In conclusion, although sequellae should be evaluated over a long-term period, implantation of a new 2.9 Fr reservoir system is technically feasible and useful in performing arterial infusion chemotherapy.

Aged↗

PubMed2001

Multi-functional roles of Stat3 revealed by conditional gene targeting.

Signal transducer and activator of transcription (STAT) is a family of transcription factors composed of seven members. Gene-targeted mice of each STAT family protein displayed defective responses to cytokines, demonstrating an important role in cytokine-mediated biological responses. However, unlike the mice lacking other STAT proteins, Stat3-deficient mice died during their early embryogenesis. Therefore, in an attempt to avoid the lethality and assess the role of Stat3 in cytokine-mediated functions in mouse adult tissues, conditional gene targeting utilizing a Cre-loxP system was achieved. By this method, Stat3 was disrupted in several types of tissue, including T cells, macrophages, skin, and mammary gland. Analyses of these Stat3-mutant mice revealed important roles of Stat3 in biological functions in each tissue.

Animals↗

PubMed2001

[Endotracheal intubation with a lighted stylet in a patient with difficult airway from the first and second brancheal arch syndrome].

A 28 year-old-woman with the first and second brancheal arch syndrome was scheduled for the lift of the inferior part of the right ear. Difficult intubation was expected because of the mandibular hypoplasia. We chose a lightwand stylet for tracheal intubation. Anesthesia was induced with sevoflurane slowly increased to 5% in nitrous oxide 3 l.min-1 with oxygen 3 l.min-1. A spiral tube with 6.5 mm inner diameter (Safety-Flex, Mallinckrodt Medical, Ireland) was attached to the lightwand stylet (Surch-Light, Aaron, U.S.A.) and shaped to fit to pharyngo-laryngeal curve. Under spontaneous breathing, the tube was successfully inserted without laryngoscopy. No traumatic events occurred. Usually fiberoptic laryngoscopy requires more skill, more expensive equipment, and more time to prepare than the lightwand stylet technique. Moreover profuse secretions or blood in the oropharynx sometimes inhibit clear vision by fiberoptic laryngoscopy. The lightwand stylet is simple and inexpensive and it is useful for tracheal intubation in patients with difficult airway from the first and second brancheal arch syndrome.

Abnormalities, Multiple↗

PubMed2001

[Increased serum PIVKA-II levels in hyperthyroidism].

PIVKA-II has been practically used as a tumor marker of hepatocellular carcinoma. On the other hand, increased serum PIVKA-II concentration was reported in a Japanese patient who had hyperthyroidism without liver diseases. To evaluate whether thyroid hormone is related with serum PIVKA-II, we examined serum PIVKA-II concentrations in patients with various thyroid diseases. Eight patients with Hashimoto disease, 24 patients with Graves' disease, and 8 healthy subjects were studied. There was no significant difference of serum PIVKA-II levels among the three groups. However, serum PIVKA-II concentrations(mean +/- SD mAU/ml) in hyperthyroidism(37 +/- 27) were significantly higher than those in hypothyroidism(16 +/- 9) and normal controls(12 +/- 4) (p < 0.05 and p < 0.01, respectively). When hyperthyroid patients were treated by antithyroid drug or isotope, serum PIVKA-II concentrations decreased in accordance with the decrease of serum FT4 concentrations. Our data indicate that serum PIVKA-II concentration was increased in patients with hyperthyroidism, but further in vivo studies are necessary to clarify the mechanism related to increased serum PIVKA-II by thyroid hormone.

Adolescent↗

PubMed2001

[Current advances and expectations in tumor immunology].

Natural killer (NK) cells and Interferon (IFN)-gamma have been implicated in immune surveillance against tumor. We demonstrated the critical role of perforin in NK cell-mediated cytotoxic activity and anti-tumor effect in IFN-gamma inducible IL-12. And, we recently reported that TRAIL is constitutively expressed on a substantial proportion of murine NK cells in the liver, and which is responsible for spontaneous cytotoxicity and the anti-metastatic activity against TRAIL-sensitive tumor cells along with perforin and Fas ligand. Interestingly, the TRAIL expression on liver NK cells appeared to be regulated by endogenously produced IFN-gamma. Consisting with this finding, IL-12 and NKT cell specific ligand, alpha-Galactosylceramide (alpha-GalCer), induced TRAIL-mediated cytotoxcity and anti-tumor effect, and which was mediated by TRAIL expressed on IFN-gamma-activated NK cells. Tumor necrosis factor(TNF)-related apoptosis-inducing ligand (TRAIL) is a type II transmembrane protein belonging to the TNF family, which preferentially induces apoptotic cell death in various tumor cells in vitro. Preclinical studies in mice and nonhuman primates have shown that administration of recombinant soluble forms of TRAIL could suppress the growth of TRAIL-sensitive tumor xenografts with no apparent systemic toxicity. These studies suggested a potential utility of TRAIL as a cancer therapeutic, although TRAIL expression at protein levels and its physiological roles in tumor surveillance has remained unknown. Presented findings provide the first evidence for the physiological function of TRAIL as a tumor suppressor.

Animals↗

PubMed2001

[Coronary artery dissection following angioplasty evaluated by fractional flow reserve: report of three cases].

Fractional flow reserve was measured in three patients with coronary artery dissection occurring after percutaneous coronary intervention. In Case 1, fractional flow reserve decreased from 0.88 to 0.73 and angiography showed coronary artery dissection 20 min after balloon angioplasty. In Case 2, angiography showed good results, but the fractional flow reserve decreased to a low value(0.69). Intravascular ultrasonography revealed dissection. In Case 3, angiography clearly showed dissection, but fractional flow reserve remained high(0.91). Stent implantation was performed in all three patients, but might not have been necessary in Case 3. Dissection with low or diminished fractional flow reserve value may cause a pressure gradient in the true lumen. Stent implantation is necessary in such cases. On the other hand, cases of dissection in which the fractional flow reserve value is maintained may also cause a pressure gradient in true lumen, but stent implantation may not be necessary. Fractional flow reserve measurements may be useful for the assessment of coronary artery dissection and evaluating the indications for stent implantation.

Aortic Dissection↗

PubMed2001

Regulation of innate immune responses by Toll-like receptors.

Innate immune response in Drosophila is mediated by signaling through Toll receptors. In mammals, Toll-like receptors (TLRs), comprising a large family, recognize a specific pattern of microbial components. So far, the roles of TLR2, TLR4, TLR5, TLR6, and TLR9 have been revealed. The recognition of microbial components by TLRs leads to activation of innate immunity, which provokes inflammatory responses and finally the development of adaptive immunity. The inflammatory response depends on a TLR-mediated MyD88-dependent cascade. However, there seems to exist additional cascades in TLR signaling. In the case of TLR4 signaling, an MyD88-independent pathway is now being characterized. In addition to the activation of innate immune responses, TLR-mediated signaling leads to suppression of the activity of innate immune cells, represented by "lipopolysaccharide (LPS) tolerance". Progress in elucidating the molecular mechanisms for LPS tolerance has been made through the analysis of TLR-mediated signaling pathways. Thus, the activity for innate immune responses is known to be finely regulated by TLRs.

Adaptor Proteins, Signal Transducing↗

PubMed2000

Mechanism of calcium oscillations in migrating human astrocytoma cells.

Numerous studies show that intracellular calcium controls the migration rate of different mobile cell types. We studied migrating astrocytoma cells from two human cell lines, U-87MG and A172, in order to clarify the mechanisms by which calcium potentially influences cell migration. Using the wound-healing model to assay migration, we showed that four distinct components of migration could be distinguished: (i) a Ca(2+)/serum-dependent process; (ii) a Ca(2+)-dependent/serum-independent process; (iii) a Ca(2+)/serum-independent process; (iv) a Ca(2+)-independent/serum-dependent process. In U-87MG cells which lack a Ca(2+)-dependent/serum-independent component, we found that intracellular Ca(2+) oscillations are involved in Ca(2+)-dependent migration. Removing extracellular Ca(2+) greatly decreased the frequency of migration-associated Ca(2+) oscillations. Furthermore, non-selective inhibition of Ca(2+) channels by heavy metals such as Cd(2+) or La(3+) almost completely abolished changes in intracellular Ca(2+) observed during migration, indicating an essential role for Ca(2+) channels in the generation of these Ca(2+) oscillations. However, specific blockers of voltage-gated Ca(2+) channels, including nitrendipine, omega-conotoxin GVIA, omega-conotoxin MVIIC or low concentrations of Ni(2+) were without effect on Ca(2+) oscillations. We examined the role of internal Ca(2+) stores, showing that thapsigargin-sensitive Ca(2+) stores and InsP(3) receptors are involved in Ca(2+) oscillations, unlike ryanodine-sensitive Ca(2+) stores. Detailed analysis of the spatio-temporal aspect of the Ca(2+) oscillations revealed the existence of Ca(2+) waves initiated at the leading cell edge which propagate throughout the cell. Previously, we have shown that the frequency of Ca(2+) oscillations was reduced in the presence of inhibitory antibodies directed against beta3 integrin subunits. A simple model of a Ca(2+) oscillator is proposed, which may explain how the generation of Ca(2+) oscillations is linked to cell migration.

Astrocytoma↗

PubMed2000

Novel activation of non-selective cationic channels by dinitrosyl iron-thiosulfate in PC12 cells.

Low molecular mass dinitrosyl iron complexes (DNICs) are nitrosating agents and it is known that the dinitrosyl iron moiety can be transferred to proteins. The aim of the present study was to determine if the formation of protein-bound dinitrosyl iron can modulate ionic channel activity. In PC12 cells, dinitrosyl iron-thiosulfate (50 microM) caused irreversible activation of a depolarizing inward current (IDNIC). IDNIC was partially inhibited by the metal chelator diethyldithiocarbamate (DETC, 1 mM), but not by the reducing/denitrosylating agent dithiothreitol (DTT, 5 mM). The activation of IDNIC was not reproduced by application of nitric oxide (NO., 100 microM), S-nitrocysteine (200 microM) or ferrous iron-thiosulfate (50 microM), and was not prevented by the irreversible guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo-[4, 3-a]quinoxalin-1-one (ODQ, 1 microM). Similarly, intracellular perfusion of dinitrosyl iron-thiosulfate (100 microM) did not result in activation of IDNIC. Ion replacement experiments show that the DETC-sensitive component of IDNIC is a non-selective cationic current. In accordance, IDNIC was blocked by antagonists of receptor-operated calcium entry, gadolinium (25 microM) and SK&F 96365 (25 microM). Single-channel measurements from outside-out patches reveal that the DETC-sensitive component of IDNIC is an inward current carried by a cationic channel having a conductance of 50 pS. The present observations suggest that the formation of ion channel-bound dinitrosyl iron represents another mechanism of regulation of ion channel activity by NO.-related species, which may be particularly important in pathophysiological processes where NO. is overproduced.

Animals↗

PubMed2000

Synergy and cross-tolerance between toll-like receptor (TLR) 2- and TLR4-mediated signaling pathways.

A family of Toll-like receptor (TLR) mediates the cellular response to bacterial cell wall components; murine TLR2 and TLR4 recognize mycoplasmal lipopeptides (macrophage-activating lipopeptides, 2 kDa (MALP-2)) and LPS, respectively. Costimulation of mouse peritoneal macrophages with MALP-2 and LPS results in a marked increase in TNF-alpha production, showing the synergy between TLR2- and TLR4-mediated signaling pathways. Macrophages pretreated with LPS show hyporesponsiveness to the second LPS stimulation, termed LPS tolerance. The LPS tolerance has recently been shown to be primarily due to the down-regulation of surface expression of the TLR4-MD2 complex. When macrophages were treated with MALP-2, the cells showed hyporesponsiveness to the second MALP-2 stimulation, like LPS tolerance. Furthermore, macrophages pretreated with MALP-2 showed reduced production of TNF-alpha in response to LPS. LPS-induced activation of both NF-kappaB and c-Jun NH(2)-terminal kinase was severely impaired in MALP-2-pretreated cells. However, MALP-2-pretreated macrophages did not show any reduction in surface expression of the TLR4-MD2 complex. These findings indicate that LPS-induced LPS tolerance mainly occurs through the down-regulation of surface expression of the TLR4-MD2 complex; in contrast, MALP-2-induced LPS tolerance is due to modulation of the downstream cytoplasmic signaling pathways.

Animals↗

PubMed2000

Antioxidant effect of estrogen on cytomegalovirus-induced gene expression in coronary artery smooth muscle cells.

BACKGROUND: Pathogens infecting the arterial wall with resultant inflammation may contribute to atherogenesis. Human coronary artery smooth muscle cells (SMCs) infected with human cytomegalovirus (CMV) demonstrate a rapid increase in reactive oxygen species (ROSs), with activation of genes involved in viral replication and inflammation. Because estrogen appears to have antioxidant properties, we wished to determine whether this hormone attenuates SMC responses to CMV infection. METHODS AND RESULTS: Using confocal microscopy and an intracellular fluorescent dye activated by ROSs, we found that 17beta-estradiol (0.1 to 10 nmol/L) and its stereoisomer 17alpha-estradiol (which has low affinity for the estrogen receptor) dose-dependently inhibited ROS generation in CMV-infected SMCs. These effects were not blocked by the estrogen receptor inhibitor ICI 182,780. 3-Methoxyestrone, which lacks the phenolic hydroxyl group, did not interfere with ROS generation. We found that 17beta-estradiol and 17alpha-estradiol, but not 3-methoxyestrone, prevented binding of nuclear factor (NF)-kappaB to DNA. Furthermore, in SMCs transfected with the reporter constructs 3XkappaB-CAT, MIEP-CAT, or ICAM-CAT, cotransfection with a CMV-IE72 expression plasmid caused promoter and CAT activation. Treatment with 17beta-estradiol and 17alpha-estradiol, but not 3-methoxyestrone, inhibited CAT activity and, in CMV-infected SMCs, prevented IE72 and ICAM-1 protein expression and cytopathic effects. CONCLUSIONS: These findings indicate that estrogen molecules with an A-ring hydroxyl group have estrogen receptor-independent anti-CMV effects at physiological concentrations by inhibiting ROS generation, NF-kappaB activation, NF-kappaB-dependent transcription, and viral replication. To the extent that chronic infection of the vascular wall with CMV contributes to atherogenesis, these antioxidant actions of estrogen may be of therapeutic importance.

Adult↗

PubMed2000

Expression of the Sox10 gene during mouse inner ear development.

Mutations in the SOX10 gene, encoding a cell-lineage specific transcription factor, are associated with congenital deafness. We analyzed the expression of Sox10 mRNA in developing mouse inner ear by in situ hybridization. Sox10 mRNA is expressed in the entire epithelia of the otic vesicle at embryonic day 11.5 (E11.5) and in the developing cochlea and vestibule at E13.5. In postnatal day 8 and adult cochleas, Sox10 expression is restricted to the supporting cells of the organ of Corti. These expression profiles suggest that Sox10 is important for development of the cochlea.

Animals↗

PubMed2000

Membrane localization of cyclic nucleotide phosphodiesterase 3 (PDE3). Two N-terminal domains are required for the efficient targeting to, and association of, PDE3 with endoplasmic reticulum.

Subcellular localization of cyclic nucleotide phosphodiesterases (PDEs) may be important in compartmentalization of cAMP/cGMP signaling responses. In 3T3-L1 adipocytes, mouse (M) PDE3B was associated with the endoplasmic reticulum (ER) as indicated by its immunofluorescent colocalization with the ER protein BiP and subcellular fractionation studies. In transfected NIH 3006 or COS-7 cells, recombinant wild-type PDE3A and PDE3B isoforms were both found almost exclusively in the ER. The N-terminal portion of PDE3 can be arbitrarily divided into region 1 (aa 1-300), which contains a large hydrophobic domain with six predicted transmembrane helices, followed by region 2 (aa 301-500) containing a smaller hydrophobic domain (of approximately 50 aa). To investigate the role of regions 1 and 2 in membrane association, we examined the subcellular localization of a series of catalytically active, Flag-tagged N-terminal-truncated human (H) PDE3A and MPDE3B recombinants, as well as a series of fragments from regions 1 and 2 of MPDE3B synthesized as enhanced green fluorescent (EGFP) fusion proteins in COS-7 cells. In COS-7 cells, the localization of a mutant HPDE3A, lacking the first 189 amino acids (aa) and therefore four of the six predicted transmembrane helices (H3A-Delta189), was virtually identical to that of the wild type. M3B-Delta302 (lacking region 1) and H3A-Delta397 (lacking region 1 as well as part of region 2) retained, to different degrees, the ability to associate with membranes, albeit less efficiently than H3A-Delta189. Proteins that lacked both regions 1 and 2, H3A-Delta510 and M3B-Delta604, did not associate with membranes. Consistent with these findings, region 1 EGFP-MPDE3B fusion proteins colocalized with the ER, whereas region 2 EGFP fusion proteins were diffusely distributed. Thus, some portion of the N-terminal hydrophobic domain in region 1 plus a second domain in region 2 are important for efficient membrane association/targeting of PDE3.

3',5'-Cyclic-AMP Phosphodiesterases↗