Author/Editor		Fanin, Marina; Nascimberi, Anna Chiara; Fulizio, Luigi; Trevisan, Carlo Pietro; Meznarič-Petruša, Marija; Angelini, Corrado
Title		Loss of calpain-3 autoacatalytic activity in LGMD2A patients with normal protein expression
Type		članek
Source		Am J Pathol
Vol. and No.		Letnik 163, št. 5
Publication year		2003
Volume		str. 1929-36
Language		eng
Abstract		The diagnosis of limb girdle muscular dystrophy (LGMD) type 2A (due to mutations in the gene encoding for calpain-3) is currently based on protein amlysis, but mutant patients with normal protein expression have also been identified. In this study we investigated 150 LGMD patients with normal calpain-3 protein expression, identified gene mutations by an allele-specific polymerase chain reaction test, and analyzed the mutant calpain-3 catalytic activity. Four different mutations were found in eight patients (5.5%): a frame-shifting deletion (550 A del) and three missense (R490Q, R489Q, R490W). Patients with normal calpin3 protein expression on Western blot are a considerable proportion (20%) of our total LGMD2A population. While in control muscle the calpain-3 Ca2++-dependent autocatatytic activity was evident within 5 minutes and was prevented by ethylene diaminetetraacetic acid, in all mutant patient samples the proteln was not degraded, indicating that the normal autocatalytic function had been lost. By this new functional test, we show that conventional protein diagnosis fails to detect some mutant proteins, and prove the pathogenetic role of R490Q, R489Q, R490W missense mutations. We suggest that these mutations impair protein activity by affecting interdomain protein interaction, or reduce autocatalytic activity by lowering the Ca++ sensitivity.
Descriptors		MUSCULAR DYSTROPHY CALPAIN CATALYSIS MUTATION ALLELES BIOPSY MICROSCOPY, ELECTRON POLYMERASE CHAIN REACTION BLOTTING, WESTERN