Altered membrane NTPase activity in Lesch-Nyhan disease fibroblasts: comparison with HPRT knockout mice and HPRT-deficient cell lines

Autor: Cibele S. Pinto, Roland Seifert, Thomas L. Shirley, Hyder A. Jinnah, William L. Nyhan
Rok vydání: 2005
Předmět:
Zdroj: Journal of Neurochemistry. 93:1579-1586
ISSN: 1471-4159
0022-3042
DOI: 10.1111/j.1471-4159.2005.03151.x
Popis: Lesch–Nyhan disease (LND) is a rare disorder caused by a defect of an enzyme in the purine salvage pathway, hypoxanthine phosphoribosyl transferase (HPRT). It is still unknown how the metabolic defect translates into the complex neuropsychiatric phenotype characterized by self-injurious behavior, dystonia and mental retardation. There are abnormalities in purine and pyrimidine nucleotide content in HPRT-deficient cells. We hypothesized that altered nucleotide concentrations in HPRT deficiency change G-protein-mediated signal transduction. Therefore, our original study aim was to examine the high-affinity GTPase activity of G-proteins in membranes from primary human skin and immortalized mouse skin fibroblasts, rat B103 neuroblastoma cells and mouse Neuro-2a neuroblastoma cells. Unexpectedly, in membranes from human fibroblasts, B103- and Neuro-2a cells, Vmax of low-affinity nucleoside 5′-triphosphatase (NTPase) activities was decreased up to 7-fold in HPRT deficiency. In contrast, in membranes from mouse fibroblasts, HPRT deficiency increased NTPase activity up to 4-fold. The various systems analyzed differed from each other in terms of Km values for NTPs, absolute Vmax values and Ki values for nucleoside 5′-[β,γ-imido]triphosphates. Our data show that altered membrane NTPase activity is a biochemical hallmark of HPRT deficiency, but species and cell-type differences have to be considered. Thus, future studies on biochemical changes in LND should be conducted in parallel in several HPRT-deficient systems.
Databáze: OpenAIRE
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