Multicenter study of intravenous busulfan, cyclophosphamide, and etoposide (i.v. Bu/Cy/E) as conditioning regimen for autologous stem cell transplantation in patients with non-Hodgkin's lymphoma

The current study aimed to evaluate the efficacy and toxicity of a combination of intravenous busulfan, cyclophosphamide and etoposide (i.v. Bu/Cy/E) as a conditioning regimen prior to autologous hematopoietic stem cell transplantation in patients with non-Hodgkin's lymphoma (NHL). Sixty-four patients with relapsed/refractory (n=36) or high-risk (n=28) lymphoma were enrolled. The high-dose chemotherapy consisted of i.v. Bu (0.8 mg kg(-1) i.v. q 6 h from day -7 to day -5), Cy (50 mg kg(-1) i.v. on day -3 and day -2) and E (400 mg m(-2) i.v. on day -5 and day -4). The median age was 43 (range 18-65) years, and 39 patients were male. Diffuse large B-cell lymphoma (40.6%) was the most common histological subtype. All evaluable patients achieved an engraftment of neutrophils (median, day 12) and platelets (median, day 13). Hepatic veno-occlusive disease was observed in four patients (three mild, one moderate grade), and two patients (3.1%) died from treatment-related complications. At a median follow-up of 16.4 months, 15 patients (23.4%) exhibited a relapse or progression, while 13 patients (20.3%) had died of disease. The estimated 3-year overall and progression-free survival for all patients was 72.1 and 70.1%, respectively. In conclusion, the conditioning regimen of i.v. Bu/Cy/E was well tolerated and seemed to be effective in patients with aggressive NHL.

New myeloablative conditioning regimen with fludarabine and busulfan for allogeneic stem cell transplantation: comparison with BuCy2

A regimen of busulfan and cyclophosphamide (BuCy2) is regarded as the standard myeloablative regimen for SCT. This study evaluated the hypothesis that fludarabine can replace cyclophosphamide for myeloablative allogeneic SCT. Ninety-five patients underwent allogeneic SCT from HLA-identical donors, following BuCy2 (n=55) or busulfan+fludarabine (BF, n=40). The efficacy of fludarabine compared to cyclophosphamide was retrospectively evaluated. The BF group exhibited a shorter duration until engraftment (P=0.001), lower incidence of acute and chronic GVHD (P<0.001 and P=0.003, respectively), and non-relapse mortality (NRM) (P=0.039). Furthermore, the event-free survival and overall survival were significantly higher for the BF group compared to the BuCy2 group (P=0.004 and 0.002, respectively). After adjusting for age, the risk status of disease, GVHD prophylaxis and donor type, the BF regimen was found to be an independent favorable risk factor for event-free survival (hazard ratio (HR), 0.181; 95% confidence interval, 0.045-0.720; P=0.016) and overall survival (HR, 0.168; 0.035-0.807; P=0.026). The replacement of cyclophosphamide with fludarabine for myeloablative conditioning seems to be more effective in terms of short-term NRM, and GVHD compared to BuCy2 regimen in allogeneic transplantation.

Novel liver-specific organic anion transporter OAT7 that operates the exchange of sulfate conjugates for short chain fatty acid butyrate

The liver plays an important role in the elimination of endogenous and exogenous lipophilic organic compounds from the body, which is mediated by various carrier proteins that differ in substrate specificity and kinetic properties. Here, we have characterized a novel member of the organic anion transporter family (SLC22) isolated from human liver. The transporter named organic anion transporter 7 (OAT7/ SLC22A9) showed 35% to 46% identities to those of other organic anion transporters of SLC22 family. When expressed in Xenopus oocytes, OAT7 mediated Na(+)-independent, high-affinity transport of sulfate-conjugated steroids, estrone sulfate (ES; K(m) = 8.7 microM), and dehydroepiandrosterone sulfate (K(m) = 2.2 microM). In addition, OAT7 interacted with negatively charged sulfobromophthalein, indocyanine green, and several sulfate-conjugated xenobiotics. In contrast, glucuronide and glutathione conjugates exhibited no inhibitory effects on OAT7-mediated [(3)H]ES transport. OAT7-mediated [(3)H]ES transport was trans-stimulated by three-carbon to five-carbon (C3 to C5) short-chain fatty acids. The efflux of [(14)C]butyrate (C4) via OAT7 was significantly trans-stimulated by extracellular ES. Furthermore, OAT7 mediated [(14)C]butyrate uptake and [(3)H]ES efflux in exchange for extracellular butyrate both in Xenopus oocytes and OAT7-stably expressing cells. OAT7 protein was localized in the sinusoidal membrane of hepatocytes by immunohistochemical analysis.

CONCLUSION

OAT7 is the first liver-specific transporter among members of the organic anion transporters of SLC22 family. Our findings suggest a new class of substrates for organic anion transporters and provide evidence for the transport of anionic substances such as sulfate-conjugates in exchange for butyrate in hepatocytes.

Identification and Functional Characterization of Genetic Variants of Human Organic Cation Transporters in a Korean Population

Genetic variants of three human organic cation transporter genes (hOCTs) were extensively explored in a Korean population. The functional changes of hOCT2 variants were evaluated in vitro, and those genetic polymorphisms of hOCTs were compared among different ethnic populations. From direct DNA sequencing, 7 of 13 coding variants were nonsynonymous single-nucleotide polymorphisms (SNPs), including four variants from hOCT1 (F160L, P283L, P341L, and M408V) and three from hOCT2 (T199I, T201M, and A270S), whereas 6 were synonymous SNPs. The linkage disequilibrium analysis presented for three independent LD blocks for each hOCT gene showed no significant linkage among all three hOCT genes. The transporter activities of MDCK cells that overexpress the hOCT2-T199I, -T201M, and -A270S variants showed significantly decreased uptake of [(3)H]methyl-4-phenylpyridinium acetate (MPP(+)) or [(14)C]tetraethylammonium compared with those cells that overexpress wild-type hOCT2, and the estimated kinetic parameters of these variants for [(3)H]MPP(+) uptake in oocytes showed a 2- to 5-fold increase in K(m) values and a 10- to 20-fold decrease in V(max) values. The allele frequencies of the five functional variants hOCT1-P283L, -P341L, and hOCT2-T199I, -T201M, and -A270S were 1.3, 17, 0.7, 0.7, and 11%, respectively, in a Korean population; the frequency distributions of these variants were not significantly different from those of Chinese and Vietnamese populations. These findings suggest that genetic variants of hOCTs are not linked among three genes in a Korean population, and several of the hOCT genetic variants cause decreased transport activity in vitro compared with the wild type, although the clinical relevance of these variants remains to be evaluated.

Cavernous haemangioma of the breast

Vascular tumours of the breast are rare and most can be classified as either angiosarcomas or haemangiomas. Cavernous haemangiomas are the most common form of mammary haemangioma. We describe a case with unilateral whole breast involvement without associated calcifications, studied with mammography, ultrasound and MRI.

Phase II study of capecitabine and irinotecan combination chemotherapy in patients with advanced gastric cancer

The present study was conducted to evaluate the efficacy and safety of a combination regimen of capecitabine plus irinotecan in patients with advanced gastric cancer. Patients with previously untreated metastatic or recurrent, measurable gastric cancer received oral capecitabine 1000 mg m⁻² twice daily from day 1 to 14 and intravenous irinotecan 100 mg m⁻² on days 1 and 8, based on a 3-week cycle. Forty-one patients were enrolled in the current study, among whom 38 were assessable for efficacy and 40 assessable for toxicity. Three complete responses and 16 partial responses were confirmed, giving an overall response rate of 46.3%. At a median follow-up of 269 days, the median time to progression and overall survival were 5.1 and 8.6 months, respectively. Grade 3/4 neutropenia occurred in four patients and grade 3 febrile neutropenia was observed in two patients. Grade 3 diarrhoea and grade 2 hand–foot syndrome occurred in six patients and eight patients, respectively. The combination of capecitabine and irinotecan was found to be well tolerated and effective in patients with advanced gastric cancer. Accordingly, this regimen can be regarded as one of first-line treatment options for advanced gastric cancer.

The PDZ domain protein PDZK1 interacts with human peptide transporter PEPT2 and enhances its transport activity

The proton-coupled peptide transporter PEPT2 (SLC15A2) mediates the high-affinity low-capacity transport of small peptides as well as various oral peptide-like drugs in the kidney. In contrast to its well-characterized transport properties, there is less information available on its regulatory mechanism, although the interaction of PEPT2 to the PDZ (PSD-95, DglA, and ZO-1)-domain protein PDZK1 has been preliminarily reported. To examine whether PDZK1 is a physiological partner of PEPT2 in kidneys, we started from a yeast two-hybrid screen of a human kidney cDNA library with the C-terminus of PEPT2 (PEPT2 C-terminus (PEPT2-CT)) as bait. We could identify PDZK1 as one of the positive clones. This interaction requires the PDZ motif of PEPT2-CT detected by a yeast two-hybrid assay, in vitro binding assay and co-immunoprecipitation. The binding affinities of second and third PDZ domains of PDZK1 to PEPT2-CT were measured by surface plasmon resonance. Co-immunoprecipitation using human kidney membrane fraction and localization of PEPT2 in renal apical proximal tubules revealed the physiological meaning of this interaction in kidneys. Furthermore, we clarified the mechanism of enhanced glycylsarcosine (Gly-Sar) transport activity in PEPT2-expressing HEK293 cells after the PDZK1 coexpression. This augmentation was accompanied by a significant increase in the V(max) of Gly-Sar transport via PEPT2 and it was also associated with the increased surface expression level of PEPT2. These results indicate that the PEPT2-PDZK1 interaction thus plays a physiologically important role in both oligopeptide handling as well as peptide-like drug transport in the human kidney.

NEUROTOXIC PYRIDINIUM METABOLITES OF HALOPERIDOL ARE SUBSTRATES OF HUMAN ORGANIC CATION TRANSPORTERS

Two neurotoxic pyridinium metabolites of haloperidol, 4-(4-chlorophenyl)-1-[4-(4-fluorophenyl)-4-oxybutyl]pyridinium ion (HPP(+)) and 4-(4-(chlorophenyl)-1-4-(fluorophenyl)-4-hydroxybutyl-pyridinium (RHPP(+)), are formed in the liver and found in the brain. To understand how these neurotoxic pyridinium metabolites are distributed in the brain, HPP(+) and RHPP(+) were evaluated as substrates for human organic cation transporters (hOCTs). Both HPP(+) and RHPP(+) were accumulated in Caco-2 cells, and these accumulations were significantly inhibited by pretreatment with the hOCT inhibitors verapamil, cimetidine, phenoxybenzamine, and corticosterone. The contribution of each hOCT was evaluated based on measurements of the intracellular concentrations of haloperidol metabolites in Madin Darby canine kidney (MDCK) cells transfected with hOCT1, hOCT2, or hOCT3. HPP(+) accumulated in hOCT-overexpressing MDCK cells in a concentration-dependent manner, with estimated K(m) values of 0.99, 2.79, and 2.23 microM and V(max) values of 282.1, 256.1, and 400.2 pmol/min/microg protein for hOCT1, hOCT2, and hOCT3, respectively. RHPP(+) accumulated in hOCT1- and hOCT3-overexpressing MDCK cells, with estimated K(m) values of 5.15 and 8.21 microM and V(max) values of 1230.9 and 1348.6 pmol/min/microg protein for hOCT1 and hOCT3, respectively. On the other hand, RHPP(+) did not accumulate in the hOCT2-expressing MDCK cells. These results suggest that HPP(+) and RHPP(+) are substrates for hOCTs, with the exception of RHPP(+) for hOCT2. Thus, hOCTs seem to contribute to the disposition of these toxic metabolites in human subjects, although further in vivo studies are required to elucidate the involvement of hOCTs in the disposition of haloperidol pyridinium metabolites.

Modulation of Renal Apical Organic Anion Transporter 4 Function by Two PDZ Domain–Containing Proteins

Human organic anion transporter 4 (OAT4) is an apical organic anion/dicarboxylate exchanger in the renal proximal tubules and mediates high-affinity transport of steroid sulfates such as estrone-3-sulfate (E1S) and dehydroepiandrosterone sulfate. Here, two multivalent PDZ (PSD-95/Discs Large/ZO-1) proteins PDZK1 and NHERF1 were examined as interactors of OAT4 by a yeast two-hybrid assay. These interactions require the extreme C-terminal region of OAT4 and the first and fourth PDZ domains of PDZK1 and the first PDZ domain of NHERF1. These interactions were confirmed by surface plasmon resonance assays (K(D): 36 nM, 1.2 microM, and 41.7 microM, respectively). In vitro binding assays and co-immunoprecipitation studies revealed that the OAT4 wild-type but not a mutant lacking the PDZ motif interacted directly with both PDZK1 and NHERF1. OAT4, PDZK1, and NHERF1 proteins were shown to be localized at the apical membrane of renal proximal tubules. The association with PDZK1 or NHERF1 enhanced OAT4-mediated E1S transport activities in HEK293 cells (1.2- to 1.4-fold), and the deletion of the OAT4 C-terminal PDZ motif abolished this effect. The augmentation of the transport activity was accompanied by alteration in V(max) of E(1)S transport via OAT4 and was associated with the increased surface expression level of OAT4 protein. This study indicates that the functional activity of OAT4 is modulated through the PDZ interaction with the network of PDZK1 and NHERF1 and suggests that OAT4 is involved in the regulated apical organic anion handling in the renal proximal tubules, provided by the PDZ scaffold.

Multisoliton complexes moving on a cnoidal wave background

We obtain solutions of coupled nonlinear Schrodinger equations which describe multisoliton complexes moving on a cnoidal-wave background. Our method is based on the Darboux transformation, which uses Sym's solution of the associated linear equation. Solutions are presented in a matrix determinant form, matrix elements of which are expressed in terms of Jacobi's elliptic functions. Some characteristics of multisoliton complexes like widths and amplitudes are explicitly calculated.

Spatial chemical inhomogeneity and local electronic structure of Mn-doped Ge ferromagnetic semiconductors

We have investigated the chemical distributions and the local electronic structure of potential diluted magnetic semiconductor Ge0.94Mn0.06 single crystals using scanning photoelectron microscopy (SPEM), x-ray absorption spectroscopy (XAS), and photoemission spectroscopy (PES). The SPEM image shows the stripe-shaped microstructures, which arise from the chemical phase separation between the Mn-rich and Mn-depleted phases. The Mn 2p XAS shows that the Mn ions in the Mn-rich region are in the divalent high-spin Mn2+ states but that they do not form metallic Mn clusters. The Mn 3d PES spectrum exhibits a peak centered at approximately 4 eV below E(F) and the negligible spectral weight near E(F). This study suggests that the observed ferromagnetism in Ge1-xMnx arises from the phase-separated Mn-rich phase.

Solutions for solitons in nonlinear optically induced lattices

We calculate stationary configurations of superposed states "soliton + cnoidal wave lattice" of the vector nonlinear Schrödinger equation, using the Darboux transformation technique. The obtained expressions contain the Jacobi elliptic and theta functions, and are easily manageable. There are five stationary configurations, in which one of the defocusing media is stable, while those of the focusing medium are classified into two weakly unstable and two unstable. The checking of the solutions as well as the construction of their typical shapes is accomplished with the help of symbolic package MATHEMATICA.

Systematic construction of multisoliton complexes

We present a simple but powerful method for constructing multisoliton complexes of the coupled nonlinear Schrödinger equation. Our method is based on the Bäckrund-Darboux transformation. A closed form of the matrix determinant is given for multisoliton complexes, including the case of a nonvanishing background. We explicitly work out the solutions of two-, three-, and four-component coupled nonlinear Schrödinger equations.

Novel single nucleotide polymorphisms of organic cation transporter 1 (SLC22A1) affecting transport functions

Organic cation transporter OCT1 (SLC22A1) plays an essential role in absorption, distribution, and excretion of various xenobiotics including therapeutically important drugs. In the present study, we analyzed the functional properties of the single nucleotide polymorphisms (SNPs) in SLC22A1 gene found in Japanese control individuals. Four mutations resulting in the amino acid changes (F160L, P283L, R287G, and P341L) were functionally characterized in Xenopus oocyte expression system. Two new SNPs, identified in Japanese population, P283L and R287G exhibited no uptake of both [14C]TEA and [3H]MPP+, although their protein expressions were detected in the plasma membrane of the oocytes injected with their cRNAs. Uptake of [14C]TEA by P341L was reduced to 65.1% compared to wild type, whereas F160L showed no significant change in its transport activity. This study suggests that the newly found OCT1 variants will contribute to inter-individual variations leading to the differences in cationic drug disposition and perhaps certain disease processes.

Pigment-lightening effect of N,N'-dilinoleylcystamine on human melanoma cells

BACKGROUND

Cystamine and linoleic acid have been reported to reduce melanin synthesis in vitro and in vivo. N,N'-dilinoleylcystamine (DLC) is a compound of cystamine and linoleic acid connected by an ester bond.

OBJECTIVES

To investigate the effects of DLC on melanin synthesis using cultured human melanoma cells.

METHODS

Levels of total melanin, eumelanin and phaeomelanin, tyrosinase protein and tyrosinase activity in situ were measured in HM3KO melanoma cells. Changes in degree of pigmentation were quantified by image analysis and compared with absorbance values. Tyrosinase from HM3KO cells was used to measure the direct effect of DLC on DOPA and DOPAchrome production.

RESULTS

At concentrations of 1.4-14 micromol L-1, DLC reduced the pigmentation of HM3KO melanoma cells but did not affect cell growth. The visual decrease in pigmentation produced by DLC was more dramatic than the decrease in total melanin content as measured by absorbance at 500 nm. DLC treatment decreased eumelanin synthesis and increased phaeomelanin synthesis in HM3KO melanoma cells. An in situ tyrosinase assay showed that DLC inhibited tyrosinase activity, as well as the level of tyrosinase protein.

CONCLUSIONS

These results suggest that DLC has pigment-lightening effects on HM3KO melanoma cells, produced by reducing the level of eumelanin while increasing the level of phaeomelanin.

Interference of magnetic and anisotropic tensor susceptibility reflections in resonant X-ray scattering of GdB4

Resonant x-ray scattering experiments at the Gd L3 edge show interference between magnetic and anisotropic tensor susceptibility (ATS) reflections in GdB4. Energy profiles obtained from the magnetic and ATS resonances exhibited approximately 10 eV separation between the maximum resonance energies. The findings show that the Gd 5d band experienced hybridization giving rise to a significant split into isotropic lower energy band and distorted upper band states that account for the magnetic and ATS scattering, respectively.

Interactions of human organic anion transporters with diuretics

The tubular secretion of diuretics in the proximal tubule has been shown to be critical for the action of drugs. To elucidate the molecular mechanisms for the tubular excretion of diuretics, we have elucidated the interactions of human organic anion transporters (hOATs) with diuretics using cells stably expressing hOATs. Diuretics tested were thiazides, including chlorothiazide, cyclothiazide, hydrochlorothiazide, and trichlormethiazide; loop diuretics, including bumetanide, ethacrynic acid, and furosemide; and carbonic anhydrase inhibitors, including acetazolamide and methazolamide. These diuretics inhibited organic anion uptake mediated by hOAT1, hOAT2, hOAT3, and hOAT4 in a competitive manner. hOAT1 exhibited the highest affinity interactions for thiazides, whereas hOAT3 did those for loop diuretics. hOAT1, hOAT3, and hOAT4 but not hOAT2, mediated the uptake of bumetanide. hOAT3 and hOAT4, but not hOAT1 mediated the efflux of bumetanide. hOAT1 and hOAT3, but not hOAT2 and hOAT4 mediated the uptake of furosemide. In conclusion, it was suggested that hOAT1 may play an important role in the basolateral uptake of thiazides, and hOAT3 in the uptake of loop diuretics. In addition, it was also suggested that bumetanide taken up by hOAT3 and/or hOAT1 is excreted into the urine by hOAT4.

Successive double high-dose chemotherapy with peripheral blood stem cell rescue collected during a single leukapheresis round in patients with high-risk pediatric solid tumors: a pilot study in a single center

In total, 18 of 26 double high-dose chemotherapies (HDCT) in pediatric solid tumors were rescued with peripheral blood stem cells collected during a single leukapheresis round (single-harvest group, SHG). In the remaining eight HDCT, additional leukapheresis were necessary after the first HDCT (HDCT1) to rescue the second HDCT (HDCT2) (double-harvest group, DHG). Stem cell collection after HDCT1 was inefficient and delayed in patients who had received prior chemotherapy before HDCT1. The interval between HDCT1 and HDCT2 was shorter in SHG than in DHG (median 62.5 days vs 178.5 days, P-value=0.002). Hematologic recovery in HDCT2 was delayed compared to HDCT1. However, there was no difference in hematologic recovery between SHG and DHG. A high rate of treatment-related mortality (TRM) was recorded during HDCT2, but there was no evidence that the shorter interval caused a higher rate of TRM (P-value=0.454). The probability of disease-free survival at 2 years after HDCT2 in the SHG and DHG were 66.7 and 25.0%, respectively (P-value=0.031). Therefore, to administer the second HDCT earlier in double HDCT, and thus to improve the survival of patients with high-risk solid tumors, the single-harvest approach is recommended rather than the double-harvest approach.

The variables affecting nuchal skin-fold thickness in mid-trimester

OBJECTIVES

To find out variables that have an effect on the measured values of nuchal skin-fold thickness (NT) and to formulate a regression equation on the basis of those variables.

METHODS

The data on gestational age (GA), cephalic index (CI), presentation (Pr, vertex or breech), and the presence or absence of nuchal cord (NC) were collected prospectively on 548 normal singleton fetuses between 16 and 24 weeks gestation, and independent correlation of those variables with NT was calculated by multiple regression analysis and a regression equation was produced.

RESULTS

GA had positive correlation and CI had negative correlation with NT. The nuchal skin-fold was thicker among fetuses with breech presentation rather than those with vertex presentation and increased in the presence of nuchal cord. We calculated the expected NT through these observations: for fetuses presenting vertex, NT = 5.608 + 0.243GA - 0.066CI + NC* and for breech, NT = 2.803 + 0.392GA - 0.066CI + NC*.

CONCLUSIONS

This is the first report, which takes GA, CI, Pr, and NC for correlation factors with NT as a whole. These equations and further studies on determining the cutoff values of the nuchal skin-fold thickness may improve the sensitivity and specificity for the detection of Down syndrome and enable to minimize unnecessary invasive procedures such as amniocentesis or cordocentesis.

Interaction of a soliton with a continuous wave packet

We analyze the scattering of a soliton from a continuous wave packet of arbitrary shape in a fiber, theoretically as well as numerically. Solitons recover their original shapes and velocities after collisions and the effect of collisions is described by the change of velocities of solitons. The theoretical predictions based on a WKB-type approximation are in a good agreement with numerical results.

Gliofibroma with extensive calcified deposits

Gliofibroma is a rare astrocytic neoplasm of young people that shows abundant deposition of collagenous matrix around glial cells. It shares some clinical and pathologic features with desmoplastic cerebral astrocytoma of infancy or desmoplastic infantile ganglioglioma. However, histogenesis or clinical behavior of these tumors is not fully known. Here, we report a case of gliofibroma with unusual extensive calcification which complicated radiologic as well as pathologic diagnosis.

Detection of avian pneumovirus in wild Canada (Branta canadensis) and blue-winged teal (Anas discors) geese

Choanal cleft swab samples from 770 wild Canada geese (Branta canadensis) and 358 blue-winged teal (Anas discors), captured for relocation or banding, were examined for the presence of avian pneumovirus (APV) RNA by reverse transcription (RT)-polymerase chain reaction (PCR) and for virus isolation. The swab samples were pooled into groups of 5 or 10. Sixty eight of 102 (66.7%) pooled goose samples were RT-PCR positive for APV RNA. Thirteen of 52 (25.0%) pooled blue-winged teal samples were RT-PCR positive for APV RNA. APV RNA-positive samples were inoculated onto chick embryo fibroblasts (CEF) and QT-35 cells. Infectious APV was isolated from five Canada goose pooled samples in CEF and from one Canada goose pool in QT-35 cells but not from blue-winged teal.

Molecular identification of a novel carnitine transporter specific to human testis. Insights into the mechanism of carnitine recognition

l-Carnitine is an essential component of mitochondrial fatty acid beta-oxidation and plays a pivotal role in the maturation of spermatozoa within the male reproductive tract. Epididymal plasma contains the highest levels of l-carnitine found in the human body, and initiation of sperm motility occurs in parallel to l-carnitine increase in the epididymal lumen. Using a specific carrier, epididymal epithelium secretes l-carnitine into the lumen by an active transport mechanism; however, the structure-activity relationship comprising the carnitine-permeation pathway is poorly understood. We discovered a novel carnitine transporter (CT2) specifically located in human testis. Analyzing the primary structure of CT2 revealed that it is phylogenetically located between the organic cation transporter (OCT/OCTN) and anion transporter (OAT) families. Hence, CT2 represents a novel transporter family. When expressed in Xenopus oocytes, CT2 mediates the high affinity transport of l-carnitine but does not accept mainstream OCT/OCTN cationic or OAT anionic substrates. We synthesized and tested various carnitine-related compounds and investigated the physicochemical properties of substrate recognition by semi-empirical computational chemistry. The data suggest that the quaternary ammonium cation bulkiness and relative hydrophobicity be the most important factors that trigger CT2-substrate interactions. Immunohistochemistry showed that the CT2 protein is located in the luminal membrane of epididymal epithelium and within the Sertoli cells of the testis. The identification of CT2 represents an interesting evolutionary link between OCT/OCTNs and OATs, as well as provides us with an important insight into the maturation of human spermatozoa.

Host cell proteins binding to the encapsidation signal epsilon in hepatitis B virus RNA

The highly conserved encapsidation signal (epsilon) of hepatitis B viral (HBV) pregenomic RNA has been reported as an essential component for encapsidation and protein priming of HBV polymerase. Here, we report that two HBV epsilon RNA-binding host proteins (80 and 43 kDa) and a copurifying protein (100 kDa) were purified and characterized by the combined methods of UV cross-linking analysis with the epsilon RNA and column chromatography. Amino-terminal microsequencing showed that 80- and 43-kDa proteins were identified as the heterodimeric nuclear factor of activated T cells (NF90/NF45) and 100 kDa as a molecular chaperone, the GRP94. The heterodimeric factor interacted preferentially with the upper-bulge region of HBV epsilon RNA helping the HBV polymerase bind the lower-bulge region. Using in vitro protein priming analysis, the initial oligonucleotide of the protein-priming product was deduced as 5'-GAAC-3', which is the complementary sequence of both regions of DR1 and epsilon in the pregenomic RNA. Previously, we also proposed that the GRP94 was associated with HBV polymerase in the human liver cell HepG2. These results suggest that the heterodimeric factor plays an important role in the priming activity of HBV polymerase.