|Human, Mouse, Rat|
Application Methods: Immunofluorescence (Immunocytochemistry), Immunohistochemistry (Paraffin), Immunoprecipitation, Western Blotting
Background: Argininosuccinate synthetase (ASS1) catalyzes the formation of argininosuccinate from citrulline and aspartate, the rate-limiting step in the urea cycle that is responsible for the synthesis of arginine and the clearance of nitrogenous waste (1). ASS1 is ubiquitously and differentially expressed in different cell types and tissues. Mutations in ASS1 are associated with citrullinemia type I, an autosomal recessive disease characterized primarily by elevated serum and urine citrulline levels in human patients (2, 3).Loss of ASS1 expression is one of the common metabolic alterations observed in many cancers, and it is a prognostic biomarker of reduced metastasis-free survival. ASS1 deficiency leads to the dependence of extracellular arginine for survival, proliferation, and cell growth. Ariginine starvation induces autophagy and apoptosis in ASS1 deficient cells and this has been exploited as a therapeutic intervention for the tumors with loss of ASS1 expression (4, 5). Pegylated arginine deiminase (ADI-PEG20), an enzyme that degrades arginine into citrulline, causes significant growth inhibition in tumors that have lost ASS1 expression, such as hepatocellular carcinoma, breast cancer, and sarcoma (6-8).
|Human, Mouse, Rat|
Application Methods: Immunofluorescence (Frozen), Immunohistochemistry (Paraffin), Immunoprecipitation, Western Blotting
Background: Huntington's Disease (HD) is a fatal neurodegenerative disorder characterized by psychiatric, cognitive, and motor dysfunction. Neuropathology of HD involves specific neuronal subpopulations: GABA-ergic neurons of the striatum and neurons within the cerebral cortex selectively degenerate (1,2). The genetic analysis of HD has been the flagship study of inherited neurological diseases from initial chromosomal localization to identification of the gene.Huntingtin is a large (340-350 kD) cytosolic protein that may be involved in a number of cellular functions such as transcription, gastrulation, neurogenesis, neurotransmission, axonal transport, neural positioning, and apoptosis (2,3). The HD gene from unaffected individuals contains between 6 and 34 CAG trinucleotide repeats, with expansion beyond this range causing the onset of disease symptoms. A strong inverse correlation exists between the age of onset in patients and the number of huntingtin gene CAG repeats encoding a stretch of polyglutamine peptides (1,2). The huntingtin protein undergoes numerous post-translational modifications including phosphorylation, ubiquitination, sumoylation, palmitoylation, and cleavage (2). Phosphorylation of Ser421 by Akt can partially counteract the toxicity that results from the expanded polyglutamine tract. Varying Akt expression in the brain correlates with regional differences in huntingtin protein phosphorylation; this pattern inversely correlates with the regions that are most affected by degeneration in diseased brain (2). A key step in the disease is the proteolytic cleavage of huntingtin protein into amino-terminal fragments that contain expanded glutamine repeats and translocate into the nucleus. Caspase mediated cleavage of huntingtin at Asp513 is associated with increased polyglutamine aggregate formation and toxicity. Phosphorylation of Ser434 by CDK5 protects against cleavage (2,3).