Cerebral foreign body granulomas after mechanical thrombectomy: Two case reports and a review of the literature.

OBJECTIVES: A foreign body granuloma after an endovascular intervention is a rare complication. Some cases of foreign body granulomas, especially after coil embolization, have been reported. However, only four cases of foreign body granulomas after mechanical thrombectomy (MT) have previously been reported. The current study reports two cases of post-MT foreign body granulomas, including a biopsy-proven case. MATERIAL AND METHODS: Case 1: A 73-year-old woman presented with complete occlusion of the right middle cerebral artery. Cerebral angiography and MT were successfully performed with improvement in clinical symptoms. Left hemiparesis and a disturbance in attention appeared after discharge and progressed slowly. She was re-admitted to our hospital 120 days after cerebral infarction owing to foreign body granulomas diagnosed on biopsy. Case 2: A 78-year-old man presented with occlusion of the left cervical internal carotid artery and the left middle cerebral artery. Cerebral angiography, percutaneous transluminal angioplasty, and MT were successfully performed. On the 34th day, he experienced progressive consciousness disorder because of foreign body granulomas. Both cases were successfully treated with steroid therapy. RESULTS: MRI after steroid treatment showed the disappearance of most nodular lesions and improvement of the encephalopathy. CONCLUSIONS: The cause of the granuloma may be an allergic reaction to the hydrophilic polymers that peel from endovascular devices. Steroid therapy is an effective treatment; therefore, neurologists should consider this complication when neurological symptoms or signs on image appears or worsens. A reliable diagnosis is important for prompt treatment.

Amino acid homeostatic control by TORC1 in Saccharomyces cerevisiae under high hydrostatic pressure.

Mechanical stresses, including high hydrostatic pressure, elicit diverse physiological effects on organisms. Gtr1, Gtr2, Ego1 (also known as Meh1) and Ego3 (also known as Slm4), central regulators of the TOR complex 1 (TORC1) nutrient signaling pathway, are required for the growth of Saccharomyces cerevisiae cells under high pressure. Here, we showed that a pressure of 25 MPa (∼250 kg/cm2) stimulates TORC1 to promote phosphorylation of Sch9, which depends on the EGO complex (EGOC) and Pib2. Incubation of cells at this pressure aberrantly increased glutamine and alanine levels in the ego1Δ, gtr1Δ, tor1Δ and pib2Δ mutants, whereas the polysome profiles were unaffected. Moreover, we found that glutamine levels were reduced by combined deletions of EGO1, GTR1, TOR1 and PIB2 with GLN3 These results suggest that high pressure leads to the intracellular accumulation of amino acids. Subsequently, Pib2 loaded with glutamine stimulates the EGOC-TORC1 complex to inactivate Gln3, downregulating glutamine synthesis. Our findings illustrate the regulatory circuit that maintains intracellular amino acid homeostasis and suggest critical roles for the EGOC-TORC1 and Pib2-TORC1 complexes in the growth of yeast under high hydrostatic pressure.

[Anterior Interosseous Nerve Palsy with Isolated Flexion Palsy of the Thumb or Index Finger as an Initial Symptom:Two Case Reports].

Case 1: A 73-year-old man who had undergone neurolysis for right cubital tunnel syndrome complained of difficulty using chopsticks. Froment's sign test showed that the interphalangeal(IP)joint of the right thumb that had flexed preoperatively was extended. This finding was considered to indicate recovery from ulnar neuropathy, and the patient was closely followed up. One year later, the patient was unable to push a camera shutter button and was unable to flex the IP joint of the thumb and the distal interphalangeal(DIP)joint of the index finger, a characteristic symptom of anterior interosseous nerve(AIN)palsy. Therefore, the patient underwent AIN neurolysis and subsequently reported slight improvement in his condition. Case 2: A 60-year-old woman reported difficulty performing computer mouse clicks with her right hand. As flexing the index finger DIP joint was difficult, a local lesion was suspected, and the patient was closely followed up. One year later, the patient was unable to push the button of a ballpoint pen with her thumb. Extension of the thumb and index finger indicated AIN palsy. The patient refused treatment and was only followed up. The following year, the patient reported that the weakness improved. Simultaneous flexion palsy of the thumb and index finger can lead to a diagnosis of AIN palsy. However, flexion palsy of a single finger in incomplete AIN palsy, as reported here, is often overlooked because of its similarity to the flexor tendon rupture. Awareness regarding this incomplete form of AIN palsy is needed for early and correct diagnosis.

Relationship between drug formulary and frequently used cephalosporins, macrolides and quinolones in Japanese hospitals.

In Japan, hospitals' pharmaceutical affairs committees freely select the drugs to be purchased depending on the regulations of each hospital. This system poses a risk of the absence of essential drugs or an excess of similar drugs, and may promote inappropriate use of third-generation cephalosporins (3GCs) and quinolones. Against this backdrop, we researched availability of antibacterial agents in Japanese hospitals. We conducted a questionnaire-based study in eastern Shizuoka Prefecture, Japan. Questionnaires were sent to 33 hospitals that had established an interactive regional partnership on infection control. We analyzed the number of available oral cephalosporins, macrolides, and quinolones in each hospital, and the correlation between the number of total available antibacterial agents and the hospital scale and cephalexin availability. Thirty-one hospitals participated in this study. First-generation cephalosporin (1 GC) was available in only 22.5% of them. In all participating hospitals, 3GCs were available, with more than one 3 GC available in 74.2%. Quinolones were available in all hospitals, and more than one quinolone in 67.7%. The numbers of hospital beds and total available antibacterial agents were positively correlated and hospitals that owned cephalexin available also significantly more often owned other available antibacterial agents. 1 GC were available in only a few hospitals, while multiple 3GCs and quinolones were available in most. This situation may lead to excess use of 3GCs or quinolones in Japan. A low number of available drugs was associated with cephalexin unavailability. Outpatient antimicrobial stewardship may focus not only on the quality of medicine, but also on the prescribing environment.

[Lymphorrhea at the Site of Repeated Fascia Lata Harvesting:A Case Report].

This 74-year-old man had undergone a third re-operation for anaplastic meningioma in the convexity six weeks before he was referred to us. He presented with a bulge on the lateral aspect of the left thigh. We observed a fresh fascia lata harvesting scar that extended peripherally from an old proximal scar. The bulge was colorless. The aspirated subcutaneous fluid(more than 200mL)was watery and yellowish;there was no evidence of abscess or hematoma. Although the bulge shrank after aspiration and the placement of a compression bandage, it recurred in three days. Surgery-associated lymphorrhea was the diagnosis given. Goreisan, a herbal medicine for hydrostatic modulation, was administered. One week later, the bulge diminished in size. Harvesting of the fascia lata in the lateral aspect of the thigh is usually safe. However, additional dissection and peripheral extension due to repeated harvesting risks damaging the superficial lymphatic pathways because of scar formation after earlier surgeries and the hyperdense distribution of the lymphatic pathways in the peripheral part. When subcutaneous fluid collection after fascia lata harvesting is refractory, lymphorrhea must be considered in the differential diagnosis.

[Successful unrelated cord blood transplantation for extensive meningeal juvenile xanthogranuloma developing after treatment of Langerhans cell histiocytosis in a child].

A 2-year and 4-month-old boy developed Langerhans cell histiocytosis (LCH) at the left parietal region of the skull. After treatment with chemotherapy, the patient achieved remission but experienced three relapses. After 3 years, he complained of headache, blurred vision, and lethargy. Brain magnetic resonance imaging revealed multiple dura-based meningeal masses. Biopsy was performed, and the patient was then diagnosed with juvenile xanthogranuloma (JXG). The analysis of both LCH/JXG tissues revealed BRAF V600E mutation. The JXG masses were not responsive to prednisolone, which was injected locally, radiotherapy (24 Gy), and chemotherapy (2-chlorodeoxy-adenosine). In addition, since the patient developed macrophage activation syndrome associated with systemic JXG progression, he received unrelated cord blood transplantation (u-CBT) at the age of 10 years and 11 months. Engraftment was performed at day 42, and significant GVHD was not observed. Four months after CBT, the patient was treated with infliximab (Remicade®) and dexamethasone palmitate (Limethasone®). The size of the intracranial JXG masses gradually decreased after u-CBT and disappeared after 4 years. Currently, the patient is doing well at the age of 25 years and is receiving androgen replacement therapy.

Hyperactive mutation occurs adjacent to the essential glutamate 286 for transport in the yeast tryptophan permease Tat2.

In Saccharomyces cerevisiae, high-affinity tryptophan import is mediated by the plasma membrane permease Tat2. Herein, we identified hyperactive Tat2 mutations, I285V and I285T, which allowed the cells to grow at very low tryptophan concentrations (<4 µg/mL). The Km value of wild-type Tat2 for tryptophan appeared to be 24 µg/mL, whereas that of Tat2I285V and Tat2I285T was 17 and 11 µg/mL, respectively. Normalized values of Vmax/Km for Tat2I285V- and Tat2I285T-mediated tryptophan import were 2-fold higher than that for Tat2, suggesting that these mutations increase the affinity for tryptophan, and mediate transport at very low tryptophan concentrations. I285 resides adjacent to E286, a fully conserved residue among amino acid pemreases. According to a pKa prediction for E208 (pKa ∼8.3-11.7) of Escherichia coli AdiC antiporter, a structural homologue of Tat2, the E286 carboxyl chain of Tat2 could get loaded with a proton during tryptophan/H+ symport. Hence, I285V and I285T mutations might affect the buried residue environment of Tat2, thereby facilitating tryptophan import. Additionally, Tat2I285V and Tat2I285T levels increased rapidly, and were efficiently localized to the cell surface after transferring the cells to low tryptophan medium (0.5 µg/mL). Our findings provide a clue to gain insights into the property of high-affinity transport mechanisms, and offer a unique approach to improve the functionality of broad types of amino acid permeases.

[False Aneurysm Formation at the Origin of the M2 Segment of the Middle Cerebral Artery Following a Blunt Head Trauma:A Case Report].

A 43-year-old man fell from a 1m-high truck loading platform and sustained an injury in the occiput. On admission, he was alert and neurologically intact. Computed tomography(CT)showed hemorrhage in the right sylvian fissure and parenchyma adjacent to the sphenoid wing. Magnetic resonance angiography detected no abnormalities. The course was uneventful for 11 days. However, on the 12th day, he spontaneously manifested with stupor. CT and CT angiography revealed expansion of the hemorrhage and an aneurysm arising from the origin of the M2 segment of the right middle cerebral artery. After superficial temporal artery to middle cerebral artery bypass, the aneurysm, a reddish pulsatile mass, was removed from the origin of the torn M2 segment, and the laceration was sutured. The histological diagnosis was false aneurysm. He recovered and was discharged 4 months after the trauma. Traumatic cerebral aneurysms are rare in the proximal segment of the middle cerebral artery. However, they should be distinguished from nontraumatic true aneurysms in the same region and treated as false aneurysms, which are major and critical traumatic aneurysms, for favorable outcomes.

Biopsy-proven vancomycin-induced acute kidney injury: a case report and literature review.

BACKGROUND: Vancomycin is the first-line antibiotic for methicillin-resistant Staphylococcus aureus and coagulase-negative strains. The risk of vancomycin-induced acute kidney injury increases with plasma vancomycin levels. Vancomycin-induced acute kidney injury is histologically characterized by acute interstitial nephritis and/or acute tubular necrosis. However, only 12 biopsy-proven cases of vancomycin-induced acute kidney injury have been reported so far, as renal biopsy is rarely performed for such cases. Current recommendations for the prevention or treatment of vancomycin-induced acute kidney injury are drug monitoring of plasma vancomycin levels using trough level and drug withdrawal. Oral prednisone and high-flux haemodialysis have led to the successful recovery of renal function in some biopsy-proven cases. CASE PRESENTATION: We present the case of a 41-year-old man with type 1 diabetes mellitus, who developed vancomycin-induced acute kidney injury during treatment for Fournier gangrene. His serum creatinine level increased to 1020.1 µmol/L from a baseline of 79.6 µmol/L, and his plasma trough level of vancomycin peaked at 80.48 µg/mL. Vancomycin discontinuation and frequent haemodialysis with high-flux membrane were immediately performed following diagnosis. Renal biopsy showed acute tubular necrosis and focal acute interstitial nephritis, mainly in the medullary rays (medullary ray injury). There was no sign of glomerulonephritis, but mild diabetic changes were detected. He was discharged without continuing haemodialysis (serum creatinine level, 145.0 µmol/L) 49 days after initial vancomycin administration. CONCLUSIONS: This case suggests that frequent haemodialysis and renal biopsy could be useful for the treatment and assessment of vancomycin-induced acute kidney injury, particularly in high-risk cases or patients with other renal disorders.

[Formation of a Subcutaneous Amputation Neuroma after Incomplete Endoscopic Carpal Tunnel Release Resulting in Complex Regional Pain Syndrome:A Case Report].

This 64-year-old woman had undergone endoscopic carpal tunnel release(ECTR)for right carpal tunnel syndrome 16 months earlier. Thereafter, she reported persistent dysesthesia in the thumb and index finger, developed burning pain in the middle and ring finger, paleness, coldness, and edema of the hand, a decreased range in hand motion, and a painful subcutaneous nodule just distal to the portal in the forearm. Based on physical, radiological, and electrophysiological studies, the diagnosis was incomplete carpal tunnel release associated with complex regional pain syndrome(CRPS). At open revision surgery, the carpal tunnel was released completely and the nodule was removed. Symptoms other than hypesthesia in the middle and ring fingers improved. Pathologically, the nodule was an amputation neuroma. Her CRPS was attributed to ECTR complications; i.e., persistence of median nerve compression and the formation of an amputation neuroma in the palmar cutaneous branch of the ulnar nerve at the portal. Surgeons must be aware that ECTR, a less invasive technique, may result in serious complications including CRPS.

Functional analysis of human aromatic amino acid transporter MCT10/TAT1 using the yeast Saccharomyces cerevisiae.

Tryptophan is an essential amino acid in humans and an important serotonin and melatonin precursor. Monocarboxylate transporter MCT10 is a member of the SLC16A family proteins that mediates low-affinity tryptophan transport across basolateral membranes of kidney, small intestine, and liver epithelial cells, although the precise transport mechanism remains unclear. Here we developed a simple functional assay to analyze tryptophan transport by human MCT10 using a deletion mutant for the high-affinity tryptophan permease Tat2 in Saccharomyces cerevisiae. tat2Δtrp1 cells are defective in growth in YPD medium because tyrosine present in the medium competes for the low-affinity tryptophan permease Tat1 with tryptophan. MCT10 appeared to allow growth of tat2Δtrp1 cells in YPD medium, and accumulate in cells deficient for Rsp5 ubiquitin ligase. These results suggest that MCT10 is functional in yeast, and is subject to ubiquitin-dependent quality control. Whereas growth of Tat2-expressing cells was significantly impaired by neutral pH, that of MCT10-expressing cells was nearly unaffected. This property is consistent with the transport mechanism of MCT10 via facilitated diffusion without a need for pH gradient across the plasma membrane. Single-nucleotide polymorphisms (SNPs) are known to occur in the human MCT10 coding region. Among eight SNP amino acid changes in MCT10, the N81K mutation completely abrogated tryptophan import without any abnormalities in the expression or localization. In the MCT10 modeled structure, N81 appeared to protrude into the putative trajectory of tryptophan. Plasma membrane localization of MCT10 and the variant proteins was also verified in human embryonic kidney 293T cells.

Continuing efforts to standardize measured serum growth hormone values in Japan.

Determination of serum growth hormone (GH) levels is mandatory for diagnosis of GH deficiency and excess. In the present study, we, the Study Committee for GH and Its Related Factors, The Foundation for Growth Science, Japan measured GH values in serum samples using all the commercially available kits in Japan. Significant discrepancies in the GH values were observed among the kits in spite of using the unified recombinant human GH-based standards. To deal with the discrepancies, we established a formula using a linear structural relationship model and were able to standardize the GH values. We propose to use the formula to diagnose GH deficiency and excess in Japan.

Effects of financial support on treatment of adolescents with growth hormone deficiency: a retrospective study in Japan.

BACKGROUND: Treatment costs for children with growth hormone (GH) deficiency are subsidized by the government in Japan if the children meet clinical criteria, including height limits (boys: 156.4 cm; girls: 145.4 cm). However, several funding programs, such as a subsidy provided by local governments, can be used by those who exceed the height limits. In this study, we explored the impacts of financial support on GH treatment using this natural allocation. METHODS: A retrospective analysis of 696 adolescent patients (451 boys and 245 girls) who reached the height limits was conducted. Associations between financial support and continuing treatment were assessed using multiple logistic regression analyses adjusting for age, sex, height, growth velocity, bone age, and adverse effects. RESULTS: Of the 696 children in the analysis, 108 (15.5 %) were still eligible for financial support. The proportion of children who continued GH treatment was higher among those who were eligible for support than among those who were not (75.9 % vs. 52.0 %, P < 0.001). The odds ratios of financial support to continuing treatment were 4.04 (95 % confidence interval [CI]: 1.86-8.78) in boys and 1.72 (95 % CI: 0.80-3.70) in girls, after adjusting for demographic characteristics and clinical factors. CONCLUSIONS: Financial support affected decisions on treatment continuation for children with GH deficiency. Geographic variations in eligibility for financial support pose an ethical problem that needs policy attention. An appropriate balance between public spending on continuation of therapy and improved quality of life derived from it should be explored.

[Extendable Cords to Prevent Tumbling of a Suction Device during Craniotomy].

OBJECTIVE: Suction is necessary during craniotomy, and intraoperative tumbling of the suction device interrupts operative procedures. To avoid this, we developed a technique that would fasten the device to an extendable cord as is used to secure cell phones. SURGICAL TECHNIQUE: We used this technique in more than 300 craniotomies at the specific point of time when the suction device tends to tumble, i. e., during the opening and closure of a wound, which requires frequent instrument exchanges. Extendable cords fastened to the tip of the suction hose using a gift tie were attached to the drapes to secure the suction device next to the operative field. During the operation, the extendable cord followed the suction device manipulations. Consequently, although there was some tension in the cord during its extension, the maneuverability of the suction device was maintained. As the hanging suction device was closer to the operative field than devices stored in conventional pockets, its manipulation was easier and quicker. Upon release, the suction device automatically returned to its original position without distracting the surgeon. Tumbling of the device was prevented, and there were no procedure-related complications. CONCLUSIONS: Our simple modification using extendable cords prevented tumbling, avoided unnecessary replacements, and eased the manipulation of a suction device.

Functional mapping and implications of substrate specificity of the yeast high-affinity leucine permease Bap2.

Leucine is a major amino acid in nutrients and proteins and is also an important precursor of higher alcohols during brewing. In Saccharomyces cerevisiae, leucine uptake is mediated by multiple amino acid permeases, including the high-affinity leucine permease Bap2. Although BAP2 transcription has been extensively analyzed, the mechanisms by which a substrate is recognized and moves through the permease remain unknown. Recently, we determined 15 amino acid residues required for Tat2-mediated tryptophan import. Here we introduced homologous mutations into Bap2 amino acid residues and showed that 7 residues played a role in leucine import. Residues I109/G110/T111 and E305 were located within the putative α-helix break in TMD1 and TMD6, respectively, according to the structurally homologous Escherichia coli arginine/agmatine antiporter AdiC. Upon leucine binding, these α-helix breaks were assumed to mediate a conformational transition in Bap2 from an outward-open to a substrate-binding occluded state. Residues Y336 (TMD7) and Y181 (TMD3) were located near I109 and E305, respectively. Bap2-mediated leucine import was inhibited by some amino acids according to the following order of severity: phenylalanine, leucine>isoleucine>methionine, tyrosine>valine>tryptophan; histidine and asparagine had no effect. Moreover, this order of severity clearly coincided with the logP values (octanol-water partition coefficients) of all amino acids except tryptophan. This result suggests that the substrate partition efficiency to the buried Bap2 binding pocket is the primary determinant of substrate specificity rather than structural amino acid side chain recognition.

Retention of chimeric Tat2-Gap1 permease in the endoplasmic reticulum induces unfolded protein response in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, high-affinity tryptophan import is performed by subtle mechanisms involving tryptophan permease Tat2. We have shown that Tat2 requires 15 amino acid residues in the transmembrane domains (TMDs) for its import activity, whereas leucine permease Bap2 requires only seven corresponding residues for its leucine import. For this reason, the structure of Tat2 is elaborately designed to transport the hydrophobic and bulky tryptophan. Newly synthesized cell surface proteins first undergo endoplasmic reticulum (ER)-associated quality check before entering the secretory pathway. In this study, we used domain replacement with general amino acid permease Gap1 to show that Tat2 chimeric proteins were dysfunctional when TMD10 or TMD11 was replaced. These chimeras formed large 270-800-kDa protein complexes and were stably retained in the ER membrane without efficient degradation. In contrast, Tat2 chimeras of TMD9 or TMD12 retained some of their tryptophan import activity and underwent vacuolar degradation as observed with wild-type Tat2. Thus, ours results suggest that TMD10 and TMD11 are essential for the correct folding of Tat2, probably because of their interdomain interactions. Notably, overexpression of Tat2-Gap1 chimera of TMD10 activated the unfolded protein response (UPR) element-lacZ reporter, suggesting that ER retention of the protein aggregates induces the UPR.

Collagenous gastroduodenitis with recurrent gastric ulcer in 12-year-old girl.

This report describes a rare case of collagenous gastroduodenitis found in a 12-year-old Japanese girl who had recurrent hematemesis. Gastrointestinal endoscopy showed many lotus leaf-like lesions on the gastric mucosa surrounded by atrophic gastric mucosa in the antrum, with a cobblestone appearance and a scarred duodenal ulcer in the duodenal bulb. A biopsy of the gastric mucosa indicated subepithelial collagen band. The patient was treated with H2-blockers for her symptoms for 4 years following the endoscopic findings. Follow-up endoscopy showed the same appearance as before. The pathology, however, showed a more prominent subepithelial collagen deposition. To make the correct diagnosis, it is critical to know from which part the pathological biopsy specimens were taken because there were numerous collagen bands in the atrophic membrane. It is important to monitor the patient regularly for evaluation of the etiology, pathogenesis and prognosis of this rare disease.

[Modified Technique for Primary Dural Closure in the Lateral Suboccipital Approach:Dural Moisturizing with Fibrin Glue Coating].

OBJECTIVE: When employing the lateral suboccipital approach, the thin dura shrinks due to the drying effect of illumination and air exposure, and dural substitutes are often needed for closure. We developed a new technique involving dural moisturizing with fibrin glue coating that facilitates primary dural closure. PATIENTS AND METHODS: We used this technique in 12 adults who underwent the lateral suboccipital approach for 5 hemifacial spasms, 3 trigeminal neuralgias, 2 cerebellopontine meningiomas, 1 vestibular schwannoma, and 1 vertebral artery aneurysm. Fibrin glue was sprayed on the outer surface before opening the dura, and additionally sprayed on the inner surface of the reflected dural flap after opening the dura. After the intradural procedures the dura was closed with the usual knotted sutures. RESULTS: Dural closure was performed 65-340 minutes (mean: 161.9 minutes) post-durotomy. This technique resulted in primary dural closure with a sufficient area of preserved dura in all but one patient. In this patient, the dura shrank due to coagulation of the dural attachment to the meningioma for which a small autologous substitute was required. There were no procedure-related complications such as cerebrospinal fluid leakage and meningitis. CONCLUSIONS: Dural moisturizing with fibrin glue coating is simple, protects the dura from drying and shrinkage, and facilitates primary dural closure in patients undergoing the lateral suboccipital approach.

Loss of hydroxyl groups from the ceramide moiety can modify the lateral diffusion of membrane proteins in S. cerevisiae.

In the yeast Saccharomyces cerevisiae, structural diversities of complex sphingolipids [inositol phosphorylceramide (IPC), mannosylinositol phosphorylceramide, and mannosyldiinositol phosphorylceramide] are often observed in the presence or absence of hydroxyl groups on the C-4 position of long-chain base (C4-OH) and the C-2 position of very long-chain fatty acids (C2-OH), but the biological significance of these groups remains unclear. Here, we evaluated cellular membrane fluidity in hydroxyl group-defective yeast mutants by fluorescence recovery after photobleaching. The lateral diffusion of enhanced green fluorescent protein-tagged hexose transporter 1 (Hxt1-EGFP) was influenced by the absence of C4-OH and/or C2-OH. Notably, the fluorescence recovery of Hxt1-EGFP was dramatically decreased in the sur2Δ mutant (absence of C4-OH) under the csg1Δcsh1Δ background, in which mannosylation of IPC is blocked leading to IPC accumulation, while the recovery in the scs7Δ mutant (absence of C2-OH) under the same background was modestly decreased. In addition, the amount of low affinity tryptophan transporter 1 (Tat1)-EGFP was markedly decreased in the sur2Δcsg1Δcsh1Δ mutant and accumulated in intracellular membranes in the scs7Δcsg1Δcsh1Δ mutant without altering its protein expression. These results suggest that C4-OH and C2-OH are most probably critical factors for maintaining membrane fluidity and proper turnover of membrane molecules in yeast containing complex sphingolipids with only one hydrophilic head group.

Pressure-induced endocytic degradation of the Saccharomyces cerevisiae low-affinity tryptophan permease Tat1 is mediated by Rsp5 ubiquitin ligase and functionally redundant PPxY motif proteins.

Cells of Saccharomyces cerevisiae express two tryptophan permeases, Tat1 and Tat2, which have different characteristics in terms of their affinity for tryptophan and intracellular localization. Although the high-affinity permease Tat2 has been well documented in terms of its ubiquitin-dependent degradation, the low-affinity permease Tat1 has not yet been characterized fully. Here we show that a high hydrostatic pressure of 25 MPa triggers a degradation of Tat1 which depends on Rsp5 ubiquitin ligase and the EH domain-containing protein End3. Tat1 was resistant to a 3-h cycloheximide treatment, suggesting that it is highly stable under normal growth conditions. The ubiquitination of Tat1 most likely occurs at N-terminal lysines 29 and 31. Simultaneous substitution of arginine for the two lysines prevented Tat1 degradation, but substitution of either of them alone did not, indicating that the roles of lysines 29 and 31 are redundant. When cells were exposed to high pressure, Tat1-GFP was completely lost from the plasma membrane, while substantial amounts of Tat1(K29R-K31R)-GFP remained. The HPG1-1 (Rsp5(P514T)) and rsp5-ww3 mutations stabilized Tat1 under high pressure, but any one of the rsp5-ww1, rsp5-ww2, and bul1Δ bul2Δ mutations or single deletions of genes encoding arrestin-related trafficking adaptors did not. However, simultaneous loss of 9-arrestins and Bul1/Bul2 prevented Tat1 degradation at 25 MPa. The results suggest that multiple PPxY motif proteins share some essential roles in regulating Tat1 ubiquitination in response to high hydrostatic pressure.