ABSTRACT
A 28-year-old man presented to the authors' hospital with multiple intracranial tumors. At 2 years of age, he had undergone resection of a medulloblastoma and received adjunctive craniospinal irradiation. Subsequently, he was diagnosed with nevoid basal cell carcinoma syndrome, Gorlin's syndrome. Since his first presentation, he has required surgery for multiple basal cell carcinomas, an osteochondroma of the rib, two meningiomas, a trigeminal schwannoma, and a pleomorphic liposarcoma, all of which arose within the radiation field. Despite this impressive list of benign and malignant neoplasms, the patient is relatively well and leads a normal life. The authors examine the relationships between Gorlin's syndrome and radiation therapy and the subsequent development of tumors.
Subject(s)
Basal Cell Nevus Syndrome/etiology , Brain Neoplasms/etiology , Cerebellar Neoplasms/radiotherapy , Medulloblastoma/radiotherapy , Neoplasms, Radiation-Induced , Adult , Basal Cell Nevus Syndrome/diagnosis , Basal Cell Nevus Syndrome/surgery , Bone Neoplasms/surgery , Brain Neoplasms/surgery , Cerebellar Neoplasms/surgery , Humans , Liposarcoma/surgery , Male , Medulloblastoma/surgery , Neoplasms, Radiation-Induced/surgery , RibsABSTRACT
Glycation by fructose (fructation) renders bovine serum albumin more refractory to degradation by an ATP-dependent proteolytic system from reticulocytes than glycation by glucose (glucation). It appears that the decrease in the protein's susceptibility to degradation is a complex effect of the various protein-bound moities that are generated at the different stages of the Maillard reaction and not only the result of primary amino group blockage. Advanced Maillard reaction fluorescent components may induce a decrease in proteolysis, whereas the intermediate Amadori groups possibly may enhance degradation. However, the inhibitory effect on degradation of the fluorophores would predominate at higher levels of glycation. Resistance of intracellular fructated proteins to ATP-dependent degradation may lead to alterations in the function of cells with an active sorbitol pathway and, in this way, underlie the complications of diabetes.
Subject(s)
Adenosine Triphosphate/metabolism , Fructose , Glucose , Serum Albumin/chemistry , Glycation End Products, Advanced , Glycosylation , Kinetics , Maillard Reaction , Serum Albumin/metabolism , Serum Albumin, Bovine/chemistry , Serum Albumin, Bovine/metabolism , Spectrometry, Fluorescence , Glycated Serum AlbuminABSTRACT
Monoclonal antibodies (mAbs) were generated to proteasome purified from human erythrocytes. Five of six proteasome-specific mAbs reacted with three subunits in the molecular mass range of 25-28 kDa, indicating a common epitope. The other mAb (AP5C10) exhibited a more restricted reactivity, recognizing a 32-kDa subunit of the proteasome purified in its latent state. However, when the proteasome is isolated in its active state, AP5C10 reacts with a 28-kDa subunit, evidence for processing of the proteasome subunits during purification. Purified proteasome preparations which exhibited partial latency have both AP5C10 reactive subunits. Although the 32-kDa subunit appears required for latency, loss of this component and generation of the 28-kDa component are not obligatory for activation. The 32- and 28-kDa subunits can each be further resolved into three components by isoelectric focusing. The apparent loss of 4 kDa during the conversion of the 32- to 28-kDa subunit is accompanied by a shift to a more basic pI for each polypeptide. Western blots of the early steps of proteasome purification reveal an AP5C10-reactive protein at 41 kDa. This protein was separated from proteasomes by sizing chromatography and may represent a pool of precursor subunits. Since the 32-kDa subunit appears necessary for latency, it is speculated to play a regulatory role in ATP-dependent proteolytic activity.
Subject(s)
Antibodies, Monoclonal , Cysteine Endopeptidases/metabolism , Multienzyme Complexes/metabolism , Adenosine Triphosphate/metabolism , Animals , Blotting, Western , Cysteine Endopeptidases/immunology , Electrophoresis, Gel, Two-Dimensional , Electrophoresis, Polyacrylamide Gel , Humans , Mice , Mice, Inbred BALB C , Multienzyme Complexes/immunology , Proteasome Endopeptidase Complex , RadioimmunoassayABSTRACT
ATP-dependent proteolytic activities constitute a family of distinct enzymes and enzyme complexes which function in the selective degradation of proteins in the cytosol and possibly other non-lysosomal cellular compartments. In reticulocytes as well as other eukaryotic cells, conjugation of the polypeptide ubiquitin to proteins, an ATP-requiring process, is important for proteolysis. However, the popular view that ubiquitin functions by tagging substrates for recognition by conjugate-specific proteases should be viewed with caution. Evidence is reviewed implicating an ATP-independent high molecular weight protease (HMP) which can degrade non-ubiquitinated proteins in the ATP-dependent pathway. This protease consists of several related subunits based upon monoclonal antibody studies. HMP by itself, can account for effects of substrate amino group blockage on ATP-dependent proteolysis. Endogenous inhibitors (40 kDa and 50 kDa) have been isolated and shown to block HMP non-competitively. Unlike the soluble system in reticulocytes, the major ATP-dependent activity in mouse erythroleukemia cells is particulate in aqueous media but soluble in the presence of sucrose. Despite such differences, evidence suggests analogous inhibitory components in this system. The possibility that protease/inhibitor interaction is regulated by ATP and ubiquitin in different systems is discussed.
