Liver transplantation for familial amyloidotic polyneuropathy (FAP): a single-center experience over 16 years.

Orthotopic liver transplantation (LTx) is currently the only available treatment that has been proven to halt the progress of familial amyloidotic polyneuropathy (FAP). The aim of this study was to assess mortality and symptomatic response to LTx for FAP. All 86 FAP patients transplanted at our hospital between April 1990 and November 2005 were included in the study. Five patients underwent retransplantation. The 1-, 3- and 5-year patient survival rates in patients transplanted during 1996-2005 were 94.6%, 92.3% and 92.3%, respectively, a significant difference from the rates of 76.7%, 66.7% and 66.7%, respectively, during 1990-1995 (p = 0.0003). Multivariate analysis revealed that the age at the time of LTx (>or=40 years), duration of the disease (>or=7 years) and modified body mass index (mBMI) (<600) were independent prognostic factors for patient survival. A halt in the progress of symptoms was noted in most patients, but only a minority experienced an improvement after LTx. To optimize the posttransplant prognosis, LTx should be performed in the early stages of the disease, and close post-LTx monitoring of heart function by echocardiography and of heart arrhythmia by Holter ECG is mandatory.

Discordant penetrance of the trait for familial amyloidotic polyneuropathy in two pairs of monozygotic twins.

BACKGROUND: Familial amyloidotic polyneuropathy (FAP) is caused by mutated transthyretin in which valine at position 30 is substituted by methionine (ATTR Val30Met). FAP is inherited as an autosomal dominant trait with variable penetrance. CASES: Two pairs of DNA confirmed monozygotic twin brothers, 63 and 37 years of age respectively, who are heterozygous for the ATTR Val30Met gene, have been identified in Sweden. In the first twin pair (A), the onset of typical FAP symptoms occurred at the age of 48 for twin A1, whilst his twin brother (A2) is still free from FAP symptoms 13 years later. In the second pair of twins (B), the onset of polyneuropathy occurred at the age of 34 for the proband (B1), whilst his brother (B2) is healthy 3 years after the onset of his brother's disease. DISCUSSION: In the following, a detailed description of the clinical presentation of the Swedish twin pairs is provided together with a discussion of possible environmental factors initiating the onset of the disease.

Glutamate-induced currents reveal three functionally distinct NMDA receptor populations in rat dorsal horn - effects of peripheral nerve lesion and inflammation.

The importance of the N-methyl-D-aspartate (NMDA) receptor in various painful conditions is well established. The effects of peripheral nerve lesion or joint inflammation, as models of different pain states, on NMDA receptor-mediated currents and NMDA receptor subunit mRNA expression were therefore studied in acutely dissociated neurones from the rat spinal cord dorsal horn. In the neuronal population from control rats, all four NR2 subunits and both NR1 splice variants assayed were detected. A majority of neurones expressed mRNA for more than one NR2 subunit, and some neurones expressed all four NR2 subunits as well as both NR1 splice variants. The NR2B subunit was the most commonly expressed, while the NR2C was the rarest. Following nerve lesion, fewer neurones expressed NR2A compared to the control. The dose-response curve for glutamate-evoked NMDA receptor-mediated currents in the neurones was best described by a three-component fit, suggesting that three functionally distinct NMDA receptor populations are present in the dorsal horn. Minor changes in the dose-response curve after nerve lesion could not be ascribed with certainty to the lesion. Changes in other parameters of NMDA receptor-mediated currents were observed neither after nerve lesion nor after joint inflammation. In summary, the present work demonstrates that single dorsal horn neurones express mRNA for several NMDA receptor subunits. The glutamate dose-response curves indicate that there are three major types of NMDA receptors present in dorsal horn neurones. We also report a reduced expression of NR2A following peripheral nerve lesion.

Differential protein expression in rat trigeminal ganglia during inflammation.

A proteomics approach was used to investigate global protein changes in rat sensory ganglia exposed to pro-inflammatory stimuli. Inflammation was provoked in vivo by injecting selected facial areas with Freunds Complete Adjuvant (FCA), or by stimulating freshly isolated trigeminal ganglia ex vivo with pro-inflammatory mediators (interleukin-1 beta, tumor necrosis factor-alpha, interferon-gamma). Following two-dimensional gel electrophoresis, silver staining and mass spectrometry, a protein reference map and database was generated for rat trigeminal ganglia, which to our knowledge is the first to be reported. Sixty-seven out of 85 selected protein spots were successfully identified using matrix-assisted laser desorption/ionization mass spectrometry. This reference map was used to monitor changes in the ganglia proteome induced during inflammation in vivo and ex vivo. In vivo we found that FCA treatment specifically induced differential protein expression of two unidentified protein spots and, to a lower extent, of beta-tubulin. Image analysis of ganglia treated ex vivo with the cocktail of cytokines indicated that some of the changes in the protein population were also observed in vivo after FCA treatment. If the cytokine stimulation was performed in the presence of acetaminophen (paracetamol), the drug seemed to reverse the effects of cytokine treatment for at least some protein spots, restoring the same protein pattern observed in control samples.

Scavenger treatment of free radical injury in familial amyloidotic polyneuropathy: a study on Swedish transplanted and non-transplanted patients.

Since oxidative stress has been implicated in amyloid diseases, a study of scavenger treatment of hereditary transthyretin amyloidosis was undertaken on 23 familial amyloidotic polyneuropathy (FAP) patients. Nine patients had undergone a liver transplantation for the disease. Twenty patients completed the 6-month study period of scavenger treatment (vitamin C, 1 g, three times daily, vitamin E, 0.1 g, three times daily and acetylcysteine, 0.2 g three times daily). They were evaluated clinically and by immunohistochemical measurement of hydroxynonenal (HNE), a product of lipid peroxidation, in biopsy specimens. For non-transplanted patients, no improvement was found for HNE in relation to the amyloid content in biopsy specimens, whereas a tendency to a decreased amount was noted for transplanted patients. Clinically, no differences were found for non-transplanted patients, but an increased nutritional status, measured by a modified body mass index (mBMI) was noted for transplanted patients. In summary, scavenger treatment with the drugs and doses used in the present study appears to be unable to decrease lipid peroxidation in amyloid-rich tissue in non-transplanted FAP patients. For transplanted patients, lipid peroxidation tended to decrease, and the nutritional status measured by mBMI improved, even though the findings may be explained by liver transplantation alone, scavenger treatment may facilitate recovery after transplantation.

Outcome of gastrointestinal complications after liver transplantation for familial amyloidotic polyneuropathy.

BACKGROUND: Gastrointestinal disturbances are important prognostic factors for mortality and morbidity after liver transplantation for familial amyloidotic polyneuropathy (FAP). However, the impact of liver transplantation on malabsorption and bacterial small-bowel contamination has not been evaluated. METHODS: Twenty-three FAP patients were available for the study. They were examined for gastrointestinal disturbances as a part of the evaluation for liver transplantation for FAP. Bile acid malabsorption was diagnosed with the [75Se]-homocholic acid taurate (SeHCAT) test; fat malabsorption by measuring faecal fat excretion; and bacterial small-bowel contamination with the hydrogen breath test (HBT). RESULTS: No significant improvement of malabsorption test results were noted from the pre-transplant evaluation 8 months (range, 2-20 months) before transplantation to the post-transplant evaluation performed a median of 20 months (range, 9-62 months) after the procedure. The SeHCAT test result became abnormal in two patients and normal in one, and changes in the test correlated with the time the patients were waiting for transplantation. Faecal fat excretion after transplantation correlated with duration of the disease and with fat excretion before transplantation. A significantly increased fat excretion was noted at the post-transplant evaluation. A change in HBT result was noted in only one patient, in whom the test result became normal; pre-transplant values correlated with those obtained after transplantation. CONCLUSION: For most FAP patients no improvement in gastrointestinal function was found after transplantation. The finding underlines the importance of an early transplantation before the patients have developed gastrointestinal dysfunction.

Effects of thyroid hormone receptor gene disruption on myosin isoform expression in mouse skeletal muscles.

Skeletal muscle is known to be a target for the active metabolite of thyroid hormone, i.e., 3,5,3'-triiodothyronine (T(3)). T(3) acts by repressing or activating genes coding for different myosin heavy chain (MHC) isoforms via T(3) receptors (TRs). The diverse function of T(3) is presumed to be mediated by TR-alpha(1) and TR-beta, but the function of specific TRs in regulating MHC isoform expression has remained undefined. In this study, TR-deficient mice were used to expand our knowledge of the mechanisms by which T(3) regulates the expression of specific MHC isoforms via distinct TRs. In fast-twitch extensor digitorum longus (EDL) muscle, TR-alpha(1)-, TR-beta-, or TR-alpha(1)beta-deficient mice showed a small but statistically significant decrease (P < 0.05) of type IIB MHC content and an increased number of type I fibers. In the slow-twitch soleus, the beta/slow MHC (type I) isoform was significantly (P < 0. 001) upregulated in the TR-deficient mice, but this effect was highly dependent on the type of receptor deleted. The lack of TR-beta had no significant effect on the expression of MHC isoforms. An increase (P < 0.05) of type I MHC was observed in the TR-alpha(1)-deficient muscle. A dramatic overexpression (P < 0.001) of the slow type I MHC and a corresponding downregulation of the fast type IIA MHC (P < 0.001) was observed in TR-alpha(1)beta-deficient mice. The muscle- and fiber-specific differences in MHC isoform expression in the TR-alpha(1)beta-deficient mice resembled the MHC isoform transitions reported in hypothyroid animals, i.e., a mild MHC transition in the EDL, a dramatic but not complete upregulation of the beta/slow MHC isoform in the soleus, and a variable response to TR deficiency in different soleus muscle fibers. Thus the consequences on muscle are similar in the absence of thyroid hormone or absence of thyroid hormone receptors, indicating that TR-alpha(1) and TR-beta together mediate the known actions of T(3). However, it remains unknown how thyroid hormone exerts muscle- and muscle fiber-specific effects in its action. Finally, although developmental MHC transitions were not studied specifically in this study, the absence of embryonic and fetal MHC isoforms in the TR-deficient mice indicates that ultimately the transition to the adult MHC isoforms is not solely mediated by TRs.

Abdominal vessel enhancement with an ultrasmall, superparamagnetic iron oxide blood pool agent: evaluation of dose and echo time dependence at different field strengths.

RATIONALE AND OBJECTIVES: The purpose of the study was to determine the dose and echo time dependence of abdominal vessel enhancement at magnetic resonance (MR) imaging after injection of a blood pool contrast agent at two field strengths. MATERIALS AND METHODS: Sixteen healthy volunteers received NC100150 Injection at three dose levels (1.0 mg, 2.5 mg, and 4.0 mg of iron per kilogram of body weight). Images of the aorta and inferior vena cava (IVC) were obtained at 0.5 or 1.5 T. Four sequences with varying echo times were used with each subject. Signal intensities were recorded from the aorta, IVC, vessel vicinity, air, and a marker outside the patient. Contrast-to-noise ratios (CNRs) were calculated for the vessels. Aortic delineation was subjectively evaluated. RESULTS: Images with the highest mean vessel signal intensities, subjectively assessed as satisfactory for aortic delineation, were obtained with 2.5-4.0 mg of iron per kilogram of body weight at both field strengths. The highest CNR was found with 4.0 mg of iron per kilogram of body weight at 1.5 T. An increase in echo time caused larger signal intensity loss at larger dose levels. The signal intensity from the IVC was higher than that of the aorta at all dose levels, echo times, and field strengths. CONCLUSION: NC100150 Injection is an efficient T1-reducing agent at both 0.5 and 1.5 T. A positive dose response for CNR of the aorta and IVC was seen at 1.5 T.

Analysis of proteins from membrane-enriched cerebellar preparations by two-dimensional gel electrophoresis and mass spectrometry.

Two-dimensional polyacrylamide gel electrophoresis and mass spectrometry is a powerful combination for the separation of complex protein mixtures in biological samples and the subsequent identification of individual polypeptides. We have used this approach to construct a database of proteins of the porcine cerebellum, with emphasis on membrane-bound proteins, as part of our studies on the structure and function of the central nervous system. We compared the ability of different solubilization conditions (using zwitterionic and nonionic detergents; urea and thiourea) to improve the resolution of high molecular weight and hydrophobic proteins, and found the combination of 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulfonate (CHAPS), Tris, thiourea and urea to give the best results in our experiments. As a marker membrane protein, the NR1 subunit of the N-methyl D-aspartate receptor, a 120 kDa hydrophobic protein, was identified using a monoclonal antibody in combination with Western blotting. Sodium chloride treatment of the membrane preparation prior to solubilization caused further enrichment of membrane proteins. Fifty-six spots were identified using matrix-assisted laser desorption/ionization time-of-flight and nanoelectrospray mass spectrometry.

Liver transplantation in familial amyloidotic polyneuropathy (FAP). A comparative study of transplanted and non-transplanted patient's survival.

The purpose of the present study was to evaluate the impact of liver transplantation on familial amyloidotic polyneuropathy (FAP met-30) patients' survival. Forty-five FAP patients were involved in the study; 15 non-transplanted FAP patients and 30 liver-transplanted patients. All patients' records were scrutinised for information on disease duration. Preoperative nutritional status was evaluated in all patients. No difference in survival was observed for transplanted patients overall compared to historical controls. However, for cases in good nutritional status, an increased survival can be expected as a significantly increased mortality rate for malnourished patients was observed (P < 0.05). Increased survival has so far not been found for transplanted FAP patients. However, none of the transplanted cases has yet reached the expected survival time for nontransplanted FAP control patients. which is 14 years. A high fatality rate of malnourished patients transplanted late in the course of the disease contributed significantly to the mortality among transplanted patients.

Abnormal heart rate and body temperature in mice lacking thyroid hormone receptor alpha 1.

Thyroid hormone, acting through several nuclear hormone receptors, plays important roles in thermogenesis, lipogenesis and maturation of the neonatal brain. The receptor specificity for mediating these effects is largely unknown, and to determine this we developed mice lacking the thyroid hormone receptor TR alpha 1. The mice have an average heart rate 20% lower than that of control animals, both under normal conditions and after thyroid hormone stimulation. Electrocardiograms show that the mice also have prolonged QRS- and QTend-durations. The mice have a body temperature 0.5 degrees C lower than normal and exhibit a mild hypothyroidism, whereas their overall behavior and reproduction are normal. The results identify specific and important roles for TR alpha 1 in regulation of tightly controlled physiological functions, such as cardiac pacemaking, ventricular repolarisation and control of body temperature.

Effects of acute stress on the contents of catecholamines and neuropeptides in chromaffin tissues of the newborn rabbit.

The neuropeptides enkephalin (ENK), galanin (GAL) and neuropeptide Y (NPY) are abundantly expressed in the paraaortic body (PAB) and adrenal glands of the newborn rabbit. To examine whether these neuropeptides are affected by acute stress, we exposed neonatal rabbits to asphyxia, insulin-induced hypoglycemia, and reserpine. Asphyxia, caused by rebreathing for 60 min in an airtight box, reduced the content of catecholamines (CAs) in the adrenal glands and increased ENK-like immunoreactivity (-LI) in the PAB. Insulin-induced hypoglycemia reduced the content of CAs as well as ENK-LI in the adrenal glands. Reserpine caused a marked depletion of the CAs both in the PAB and in the adrenal glands. In contrast, reserpine did not cause any change in the contents of the neuropeptides in either organ. These data indicate that tissue levels of the neuropeptides GAL-LI and NPY-LI, coexisting with CA in the PAB and the adrenal glands, are not biochemically affected by asphyxia, hypoglycemia or reserpine, whereas tissue levels of ENK-LI are reduced by hypoglycemia and, to some extent, are increased by asphyxia. Furthermore, even the CAs in the PAB were unaffected by asphyxia and hypoglycemia. Also, while reserpine reduces CA content, peptide levels are unaffected.

Processing and membrane topology of the spike proteins G1 and G2 of Uukuniemi virus.

The membrane glycoproteins G1 and G2 of the members of the Bunyaviridae family are synthesized as a precursor from a single open reading frame. Here, we have analyzed the processing and membrane insertion of G1 and G2 of a member of the Phlebovirus genus, Uukuniemi virus. By expressing C-terminally truncated forms of the p10 precursor containing the whole of G1 and decreasing portions of G2, we found that processing in BHK21 cells occurred with an efficiency of about 50% if G1 was followed by 50 residues of G2, while complete processing occurred if 98, 150, or 200 residues of G2 were present. Surprisingly, processing of all truncated G2 forms was less efficient in HeLa cells. Proteinase K treatment of microsomes isolated from infected cells indicated that the C terminus of G1 is exposed on the cytoplasmic face. Using G1 tail peptide antisera, the tail was likewise found by immunofluorescence to be exposed on the cytoplasmic face in streptolysin O-permeabilized cells. By introducing stop codons at various positions of the G1 tail and at the natural cleavage site between G1 and G2 and expressing these mutants in BHK cells, we found that no further processing of the G1 C terminus occurred following cleavage of G2 by the signal peptidase. This was also supported by the finding that an antiserum raised against a peptide corresponding to the region immediately upstream from the G2 signal sequence reacted in immunoblotting with G1 from virions. Finally, we show that both G1 and G2 are palmitylated. Taken together, these results show that processing of p10 of Uukuniemi virus occurs cotranslationally at only one site, i.e., downstream of the internal G2 signal sequence. G1 and G2 are inserted as type I proteins into the lipid bilayer, leaving the G1 tail exposed on the cytoplasmic face of the membrane. Since the G2 tail is only 5 residues long, the G1 tail is likely to be responsible for the interaction with the nucleoproteins during the budding process, in addition to harboring a Golgi localization signal.

Changes in enkephalin and neuropeptide Y-like immunoreactivity in rabbit chromaffin tissues during perinatal development.

Enkephalin-like immunoreactivity (ENK-LI), neuropeptide Y (NPY)-LI and dopamine-beta-hydroxylase (DBH)-LI were found within the chromaffin cells of both the paraaortic body and the adrenal medulla of the newborn rabbit using immunohistochemistry. Cells positive to DBH-LI were abundant in both the paraaortic body and the adrenal medulla. ENK-LI positive cells were frequent in the paraaortic body, but more sparse in the adrenal medulla. A few cells staining for NPY-LI could be detected in both organs. Some nerve fibers within these organs also contained substance P-LI and calcitonin-gene related peptide-LI. The tissue contents of ENK-LI and NPY-LI, as measured by radioimmunoassay, increased after birth in the adrenal glands and were significantly higher than the fetal levels from 1 week of age. In the paraaortic body the lowest content of ENK-LI was found around birth, whereas the content of NPY-LI was highest at that time. With advancing postnatal age, the content of ENK-LI increased, whereas the content of NPY-LI decreased. At each age, there was a higher content of ENK-LI as compared to NPY-LI in both organs. This indicates that the synthesis of ENK-LI and NPY-LI in the paraaortic body is differently regulated during perinatal development.

Liver transplantation in familial amyloidotic polyneuropathy. Follow-up of the first 20 Swedish patients.

Familial amyloidotic polyneuropathy (FAP) is an inherited fatal form of amyloidosis caused by mutant transthyretin. The disease is characterized by progressive peripheral and autonomic neuropathy. Most of the transthyretin is produced by the liver, and we have shown previously that the metabolic deficiency can be corrected by liver transplantation. In the present study, the clinical results from the first 20 patients who underwent liver transplantation for FAP in Sweden are evaluated. Three of the patients suffered from renal failure and underwent a simultaneous kidney transplantation. Fourteen of the 20 patients (70%) are alive 10-52 months after transplantation. The patients' nutritional status at the time of transplantation had a significant impact on mortality and morbidity (P < 0.007). Long-standing disease was another negative prognostic factor (P < 0.02). One year after transplantation, the nutritional status had improved (P < 0.02). Improvements were also noted in walking capacity and for gastrointestinal and urogenital symptoms. The results show that liver transplantation offers an effective means to treat patients with FAP. The procedure should preferably be performed before the nutritional status is poor and advanced organ dysfunction has developed.

Multiple neuropeptide immunoreactivities in a renin-producing human paraganglioma.

BACKGROUND: A case of a renin-producing paraganglioma of adrenal origin with metastases to the retroperitoneal area, paravaginal area, and the ovary is reported with immunohistochemical findings indicating expression of multiple neuropeptide immunoreactivities. The patient was 23 years old at the time of diagnosis, and died from metastatic spread of the tumor 7 years later. METHODS: Tumor tissue was examined by light microscopy, indirect immunohistochemistry, and electron microscopy. RESULTS: The tumor tissue investigated contained several cells exhibiting opioid peptide-like immunoreactivities (i.e., enkephalin and dynorphin-like immunoreactivity [LI]). A lower number of cells displayed neuropeptide Y-, galanin-, somatostatin-, neurotensin-, substance P-, peptide histidine-isoleucine-, cholecystokinin-, renin-, and calbindin-LI. CONCLUSION: To the authors' knowledge, galanin, dynorphin, peptide histidine-isoleucine, cholecystokinin, and calbindin have not been reported previously to occur in paraganglioma, and renin has been reported to occur very rarely. A review of recent literature suggest that enkephalin-, neuropeptide Y-, and somatostatin-like immunoreactivities may be useful as diagnostic markers for paragangliomas.

Secretory pattern of vasopressin in plasma and cerebrospinal fluid of patients with dementia and of two control groups.

Since the description of its antidiuretic effect in 1913, a variety of functions have been attributed to vasopressin, one of the most controversial throughout the years probably being its effect on memory processes. In an attempt to study the actual secretory rhythm of vasopressin in humans with demonstrated impaired memory, the plasma and cerebrospinal fluid levels of the peptide have been examined during 24 h in a group of patients with dementia, and their values compared with two healthy control groups of young and elderly volunteers. Patients with dementia had higher circulating levels of vasopressin in plasma than the healthy participants and the differences were statistically significant when compared with the healthy elderly (p = 0.003). This difference is not age-related because both groups were in the same age range. A possible explanation could be the higher plasma osmolality measured in the patients with dementia, despite the fact that their levels were within the normal ranges. The different results could not be attributed to changes in electrolytes or blood pressure because these parameters were similar in all groups (p = NS). But more interesting, perhaps, is the secretory pattern found in all three groups. The pattern is biphasic, with two significant peaks: at 16.00 h (p = 0.032) and at night (p = 0.002). This pattern was similar in all cases and in all groups. The total nocturnal secretion of vasopressin is higher than the diurnal secretion (p = 0.02) only in the plasma because the cerebrospinal fluid values were higher during the day.(ABSTRACT TRUNCATED AT 250 WORDS)

Once hypertensive, always hypertensive? A three year follow-up after stopping medication.

OBJECTIVE: To verify the existence of hypertension in a group of long-term pharmacologically treated hypertensives and to evaluate the possibility of discontinuing their medication. DESIGN: The diagnosis of hypertension was established when after a wash-out period (one month) the blood pressure measured at three consecutive examinations, with at least one week interval between them, was always higher than WHO's reference levels for the diagnosis of hypertension. Those who did not fulfil these criteria would continue, with regular controls, without medication as long as clinically indicated. The final evaluation was done after a three year follow-up. SETTING: The out-patient Hypertensive Unit of the Department of Geriatrics, Skellefteå Hospital, Sweden. PARTICIPANTS: 86 out-patients (33 males and 53 females) aged 68 to 82 years (mean 74) with long-term hypertension sent to our unit by general practitioners in our health district (population 80,000). RESULTS: 34 of the initial 86 patients required medication by the end of the wash-out period. The remaining 52, 16 males and 36 females, continued without medication and after the three year follow up 14 of them were still without it. There was a striking difference between males and females since a significantly higher number of males than females were free of medication at the end of the period (p < 0.001). In those who restarted pharmacological therapy, the period without medication lasted no longer than five months. CONCLUSIONS: Arterial hypertension can easily be over-represented as a diagnosis if not revised when clinically advisable or if established without accurate criteria. The possibility of stopping the antihypertensive medication in old patients is worth considering, particularly in male patients. The dangers of such strategy are practically minimal when regular controls are undertaken during the attempt.

Unfolded H2b asialoglycoprotein receptor subunit polypeptides are selectively degraded within the endoplasmic reticulum.

When expressed alone in fibroblasts, approximately 80% of newly made H2b subunits of the human asialoglycoprotein receptor are retained and degraded in the endoplasmic reticulum (ER), whereas about 20% reaches the plasma membrane (1). Thapsigargin, an inhibitor of the ER Ca2+ ATPase, blocks ER folding of the H1 (2) as well as of the H2b subunit, prevents maturation of H2b, and accelerates ER degradation of newly made H2b. The secretory pathway is normal in thapsigargin-treated cells, as monitored by maturation of the vesicular stomatitis virus G protein. The protease inhibitors TLCK and TPCK block the first step in ER degradation of H2, an endoproteolytic cleavage just exoplasmic to the membrane-spanning domain. In protease inhibitor-treated cells, the approximately 80% of H2b that would normally be degraded remains in the ER; as judged by migration on nonreducing SDS-polyacrylamide gel electrophoresis this H2b is improperly folded. Thus, incorrectly folded H2b is normally subjected to ER degradation. In the presence of thapsigargin H2b cannot fold properly and is degraded within the ER. The preferential ER degradation of misfolded or unfolded membrane proteins demonstrated here, functions as a step in ER quality control.