Genetic variation across the human olfactory receptor repertoire alters odor perception.

Humans use a family of more than 400 olfactory receptors (ORs) to detect odors, but there is currently no model that can predict olfactory perception from receptor activity patterns. Genetic variation in human ORs is abundant and alters receptor function, allowing us to examine the relationship between receptor function and perception. We sequenced the OR repertoire in 332 individuals and examined how genetic variation affected 276 olfactory phenotypes, including the perceived intensity and pleasantness of 68 odorants at two concentrations, detection thresholds of three odorants, and general olfactory acuity. Genetic variation in a single OR was frequently associated with changes in odorant perception, and we validated 10 cases in which in vitro OR function correlated with in vivo odorant perception using a functional assay. In 8 of these 10 cases, reduced receptor function was associated with reduced intensity perception. In addition, we used participant genotypes to quantify genetic ancestry and found that, in combination with single OR genotype, age, and gender, we can explain between 10% and 20% of the perceptual variation in 15 olfactory phenotypes, highlighting the importance of single OR genotype, ancestry, and demographic factors in the variation of olfactory perception.

Agonists of G-Protein-Coupled Odorant Receptors Are Predicted from Chemical Features.

Predicting the activity of chemicals for a given odorant receptor is a longstanding challenge. Here the activity of 258 chemicals on the human G-protein-coupled odorant receptor (OR)51E1, also known as prostate-specific G-protein-coupled receptor 2 (PSGR2), was virtually screened by machine learning using 4884 chemical descriptors as input. A systematic control by functional in vitro assays revealed that a support vector machine algorithm accurately predicted the activity of a screened library. It allowed us to identify two novel agonists in vitro for OR51E1. The transferability of the protocol was assessed on OR1A1, OR2W1, and MOR256-3 odorant receptors, and, in each case, novel agonists were identified with a hit rate of 39-50%. We further show how ligands' efficacy is encoded into residues within OR51E1 cavity using a molecular modeling protocol. Our approach allows widening the chemical spaces associated with odorant receptors. This machine-learning protocol based on chemical features thus represents an efficient tool for screening ligands for G-protein-coupled odorant receptors that modulate non-olfactory functions or, upon combinatorial activation, give rise to our sense of smell.

Transient receptor potential (TRP) channels and taste sensation.

Humans have 5 basic taste sensations: sweet, bitter, sour, salty, and umami (taste of 1-amino acids). Among 33 genes related to transient receptor potential (TRP) channels, 3--including TRP-melastatin 5 (TRPM5), polycystic kidney disease-1-like 3 (PKD1L3), and polycystic kidney disease-2-like 1 (PKD2L1)--are specifically and abundantly expressed in taste receptor cells. TRP-melastatin 5 is co-expressed with taste receptors T1Rs and T2Rs, and functions as a common downstream component in sweet, bitter, and umami taste signal transduction. In contrast, polycystic kidney disease-1-like 3 and polycystic kidney disease-2-like 1 are co-expressed in distinct subsets of taste receptor cells not expressing TRP-melastatin 5. In the heterologous expression system, cells expressing both polycystic kidney disease-1-like 3 and polycystic kidney disease-2-like 1 responded to sour stimuli, showing a unique "off-response" property. Genetic ablation of poly-cystic kidney disease-2-like 1-expressing cells resulted in elimination of gustatory nerve response to sour stimuli, indicating that cells expressing polycystic kidney disease-2-like 1 function as sour taste detectors. These results suggest that polycystic kidney disease-1-like 3/polycystic kidney disease-2-like 1 may play a significant role, possibly as taste receptors, in sour taste sensation.

A candidate taste receptor gene near a sweet taste locus.

The mechanisms underlying sweet taste in mammals have been elusive. Although numerous studies have implicated G proteins in sweet taste detection, the expected G protein-coupled receptors have not been found. Here we describe a candidate taste receptor gene, T1r3, that is located at or near the mouse Sac locus, a genetic locus that controls the detection of certain sweet tastants. T1R3 differs in amino acid sequence in mouse strains with different Sac phenotypes ('tasters' versus 'nontasters'). In addition, a perfect correlation exists between two different T1r3 alleles and Sac phenotypes in recombinant inbred mouse strains. The T1r3 gene is expressed in a subset of taste cells in circumvallate, foliate and fungiform taste papillae. In circumvallate and foliate papillae, most T1r3-expressing cells also express a gene encoding a related receptor, T1R2, raising the possibility that these cells recognize more than one ligand, or that the two receptors function as heterodimers.

Bilirubin adsorption therapy and subsequent liver transplantation cured severe bilirubin encephalopathy in a long-term survival patient with Crigler-Najjar disease type I.

Crigler-Najjar disease (CN) type I is characterized by persistent unconjugated hyperbilirubinemia from birth. The male patient here was diagnosed with this disease as a neonate and had been treated by phototherapy. At age 16 he suddenly developed generalized convulsions, followed by impaired cognitive function. The serum level of bilirubin was extremely high (total bilirubin: 41.7 mg/dl) and there were no other detectable causes responsible for the metabolic encephalopathy. He received bilirubin adsorption therapy several times, and the bilirubin encephalopathy improved in response to the fall in the serum level of bilirubin. After this he underwent a successful liver transplantation in Australia, and recovery of his mental faculties was satisfactory. Within the subsequent 3 years epileptic abnormal discharges on the electroencephalogram disappeared. Phototherapy alone can not prevent the rise in the serum level of bilirubin in adolescent or adult patients with CN type I, therefore such patients tend to experience life-threatening bilirubin encephalopathy. To save patients with the acute onset type of bilirubin encephalopathy, sufficient bilirubin adsorption followed by liver transplantation appears to be the most recommended therapeutic approach.

Type II citrullinemia in an elderly patient treated with living related partial liver transplantation.

A 60-year-old woman was admitted to our hospital for repeated consciousness disturbance. Blood examination showed hyperammonemia, and plasma amino acid analysis revealed a marked increase in the citrulline level. To establish a diagnosis, a percutaneous needle biopsy of the liver was performed. The determination of the urea cycle enzyme activities revealed a selective marked decrease in argininosuccinate synthetase activity, indicating the final diagnosis of type II citrullinemia. The mean survival period of this disease after the appearance of symptoms has been reported as 26.4 months, and most conservative treatments are not effective. We performed a living related partial liver transplantation. Over the subsequent 13-month follow-up, the patient's condition has remained fairly good.

Left hemihepatectomy in living donors with a thick middle hepatic vein draining the caudal half of the right liver.

Donor safety is the first consideration in living related liver transplantation. Left hemihepatectomy including the middle hepatic vein is a reasonable donor procedure for obtaining a large graft for living related liver transplantation. This procedure, however, needs to be modified in donors with hepatic venous variation. While carrying out donor hepatectomy, we encountered two cases showing a variant form of hepatic venous drainage comprising a thick middle hepatic vein draining segment 6 of the liver. This variation made it necessary to preserve the middle hepatic vein in the donor liver remnant. Failure to recognize such a variant would result in congestion in the remaining right liver of the donor. To guarantee donor safety, evaluation of the drainage area of the corresponding hepatic vein is a matter of great importance in donor hepatectomy.

A family of candidate taste receptors in human and mouse.

The gustatory system of mammals can sense four basic taste qualities, bitter, sweet, salty and sour, as well as umami, the taste of glutamate. Previous studies suggested that the detection of bitter and sweet tastants by taste receptor cells in the mouth is likely to involve G-protein-coupled receptors. Although two putative G-protein-coupled bitter/sweet taste receptors have been identified, the chemical diversity of bitter and sweet compounds leads one to expect that there is a larger number of different receptors. Here we report the identification of a family of candidate taste receptors (the TRBs) that are members of the G-protein-coupled receptor superfamily and that are specifically expressed by taste receptor cells. A cluster of genes encoding human TRBs is located adjacent to a Prp gene locus, which in mouse is tightly linked to the SOA genetic locus that is involved in detecting the bitter compound sucrose octaacetate. Another TRB gene is found on a human contig assigned to chromosome 5p15, the location of a genetic locus (PROP) that controls the detection of the bitter compound 6-n-propyl-2-thiouracil in humans.

[Management of post liver transplantation complications].

Survival rate of liver transplanted patients is depending on management of postoperative complications. These complications include technical problems related to the operation, dysfunction of the allograft, and variety of medical complications. Differentiating and appropriately managing these diverse complications is a formidable challenge. Given the complexity of liver transplantation, it is not surprising that a variety of technical complication can occur following the operation. The most prominent of these include intraabdominal bleeding, hepatic artery thrombosis, portal vein thrombosis, and obstruction of or leak from the biliary anastomosis. In addition to these technical complications, each of which can result in dysfunction of the graft, there are a number of intrahepatic causes of graft dysfunction. The most common of these are allograft rejection, viral hepatitis and non-specific postoperative jaundice. In living related liver transplantation, primary graft non-function is rare. Accurate diagnosis and management of the various causes of graft dysfunction, whether intrahepatic or extrahepatic in origin, is very important.

Purification and characterization of 3-isopropylmalate dehydrogenase from Thiobacillus thiooxidans.

3-Isopropylmalate dehydrogenase was purified to homogeneity from the acidophilic autotroph Thiobacillus thiooxidans. The native enzyme was a dimer of molecular weight 40,000. The apparent K(m) values for 3-isopropylmalate and NAD+ were estimated to be 0.13 mM and 8.7 mM, respectively. The optimum pH for activity was 9.0 and the optimum temperature was 65 degrees C. The properties of the enzyme were similar to those of the Thiobacillus ferrooxidans enzyme, expect for substrate specificity. T. thiooxidans 3-isopropylmalate dehydrogenase could not utilize malate as a substrate.

Survival of patient with late onset hepatic failure by living-related liver transplantation from maternal donor with incompatible blood type.

A 14-year-old girl with blood type B with late onset hepatic failure (LOHF) of unknown cause has survived through living-related liver transplantation (LRLT). No hepatitis virus, including HAV, HBV, HCV, and HGV, was positive at the onset of LOHF. Autoimmune hepatitis was thought to be the cause because of positive results for serum anti-nuclear antibody at 80 times dilution and elevated gamma-globulin, but treatment with glucocorticoid did not suppress the progressive hepatic failure. Supportive therapy, including pulse therapy with 1g methylprednisolone for 3 days, ursodesoxycholic acid, branched-chain amino acid, and azathioprine did not resolve the hepatic failure. She was treated by repeated plasmapheresis and plasma absorption for 10 months, and then received the left lobe of her mother's liver. (Her mother's blood type was AB). The patient had been well, being treated with tacrolimus and prednisolone, although the serum titer of anti-blood type B antibody was high just after LRLT and mild liver dysfunction continued for more than 3 years after LRLT. Follow-up biopsy 3 years after LRLT revealed chronic hepatitis and progression to liver cirrhosis. Re-transplantation is now under consideration; the patient is now aged 19 years.

Structure of 3-isopropylmalate dehydrogenase in complex with 3-isopropylmalate at 2.0 A resolution: the role of Glu88 in the unique substrate-recognition mechanism.

BACKGROUND: 3-Isopropylmalate dehydrogenase (IPMDH) and isocitrate dehydrogenase (ICDH) belong to a unique family of bifunctional decarboxylating dehydrogenases. Although the ICDH dimer catalyzes its reaction under a closed conformation, known structures of the IPMDH dimer (without substrate) adopt a fully open or a partially closed form. Considering the similarity in the catalytic mechanism, the IPMDH dimer must be in a fully closed conformation during the reaction. A large conformational change should therefore occur upon substrate binding. RESULTS: We have determined the crystal structure of IPMDH from Thiobacillus ferrooxidans (Tf) complexed with 3-isopropylmalate (IPM) at 2.0 A resolution by the molecular replacement method. The structure shows a fully closed conformation and the substrate-binding site is quite similar to that of ICDH except for a region around the gamma-isopropyl group. The gamma group is recognized by a unique hydrophobic pocket, which includes Glu88, Leu91 and Leu92 from subunit 1 and Val193' from subunit 2. CONCLUSIONS: A large movement of domain 1 is induced by substrate binding, which results in the formation of the hydrophobic pocket for the gamma-isopropyl moiety of IPM. A glutamic acid in domain 1, Glu88, participates in the formation of the hydrophobic pocket. The C beta and C gamma atoms of Glu88 interact with the gamma-isopropyl moiety of IPM and are central to the recognition of substrate. The acidic tip of Glu88 is likely to interact with the nicotinamide mononucleotide (NMN) ribose of NAD+ in the ternary complex. This structure clearly explains the substrate specificity of IPMDH.

Involvement of R-cadherin in the early stage of glomerulogenesis.

The earliest commitment to the formation of glomeruli is recognizable in S-shaped bodies. Although cell-cell adhesion seems likely to play a crucial role in this process, how glomerular epithelial cells segregate from the other parts of the nephron is unknown. In this study, immunofluorescence microscopy and monoclonal antibodies specific for mouse R-, E-, P- and N-cadherins were used to examine which of these adhesion molecules are involved in glomerulogenesis of the mouse kidney. Weak R-cadherin staining was first found in the vesicle stage, becoming restricted to glomerular visceral epithelial cells (VEC) during the S-shaped body stage. The intensity of this staining became stronger in the capillary loop stage, whereas parietal epithelial cells (PEC) and tubular cells did not stain. In the maturing stage, VEC gradually lost their staining for R-cadherin. E-cadherin was detected in ureteric buds and the upper limb of S-shaped bodies. From the capillary loop to the maturing stage, anti-E-cadherin stained epithelial cells in all tubule segments, but no label was seen in VEC or PEC. P-cadherin was also stained in the ureteric buds and in the upper limb of S-shaped bodies. N-Cadherin was weakly stained in cells at the vesicle stage, but thereafter staining of N-cadherin was not detected at any stage of glomerular formation. Immunoelectron microscopy of differentiating VEC was performed using antibodies specific to alpha-catenin, which is associated with cadherin. Subsequently, immunogold particles identifying alpha-catenin were localized on junctions between primary processes of VEC. These findings indicate that R-cadherin is uniquely expressed in differentiating VEC, suggesting an important role in the early stages of glomerulogenesis.

Overproduction and substrate specificity of 3-isopropylmalate dehydrogenase from Thiobacillus ferrooxidans.

We constructed an overexpression system in Escherichia coli of the leuB gene coding for 3-isopropylmalate dehydrogenase in Thiobacillus ferrooxidans. E. coli harboring the plasmid we constructed, pKK leuB1, produced 17-fold the enzyme protein of the expression system previously used for purification. The substrate specificity of the enzyme was analyzed with synthetic (2R, 3S)-3-alkylmalates. The 3-isopropylmalate dehydrogenase of Thiobacillus ferrooxidans had broad specificity toward the alkylmalates.

Living related liver transplantation in adults.

OBJECTIVE: To evaluate the outcome of living related liver transplantation (LRLT) in adult patients and to assess graft size disparity and graft regeneration. SUMMARY BACKGROUND DATA: Although LRLT has been accepted as an optional life-saving procedure for pediatric patients with end-stage liver disease, the feasibility of LRLT for adult patients has not been reported with reference to a clinical series. METHODS: Adult-to-adult LRLT was performed using whole left lobar grafts in 13 patients (5 with primary biliary cirrhosis, 6 with familial amyloid polyneuropathy, 1 with biliary atresia, and 1 with citrullinemia). The 13 donors comprised 5 husbands, 3 sons, 2 sisters, 2 fathers, and 1 mother. The ratio of the graft volume to standard liver volume (GV/SV ratio) was calculated for use as a parameter of graft size disparity. RESULTS: Although the liver graft was markedly small for size (GV/SV ratio 32%-59% at the time of LRLT), none of the 13 patients developed postoperative liver failure. Eleven of the patients are still alive and well with satisfactory graft function 2 to 35 months after LRLT. Graft liver volume increased rapidly after LRLT and approximated the standard liver volume with time. CONCLUSIONS: Our LRLT program for adult patients has produced good results. LRLT in adults can be indicated for selected donor-recipient combinations.

Urgent living-related liver transplantation using a graft with multiple intrahepatic arterioportal fistulae.

BACKGROUND: We describe the case of a man with intrahepatic arterioportal fistulae located in the left lobe, whose left lateral segment was transplanted into his son who was suffering from severe acute hepatitis B. METHODS: A male infant with severe acute hepatitis B was considered to be a candidate for liver transplantation. The father was willing to be the donor. Preoperative evaluation of the donor revealed intrahepatic arterioportal fistulae, however, duplex ultrasonography showed normograde portal blood flow. A living-related liver transplantation was performed. RESULTS: The postoperative course for both the donor and recipient was uneventful. The recipient is free of recurrent hepatitis B and has normograde portal blood flow. CONCLUSIONS: The present case suggests that there may be a symptomless population with intrahepatic arterioportal fistulae, which cause various degrees of disruption of the portal blood flow. Duplex ultrasonography might be helpful in the evaluation of candidates for liver donation.