Truncated Profibrillin of a Marfan Patient is of Apparent Similar Size as Fibrillin: Intracellular Retention Leads to over-N-glycosylation

doi:10.1006/jmbi.1995.0270

Journal of Molecular Biology

Volume 248, Issue 5, 19 May 1995, Pages 901-909

https://doi.org/10.1006/jmbi.1995.0270 Get rights and content

Abstract

We studied profibrillin-1 (proFib) synthesis and microfibril formation in cultured fibroblasts from an individual with severe Marfan syndrome harboring a premature stop codon (W2756ter) in one FBN1 allele. Rotary shadowing analysis of extracellular matrix produced by these cells revealed the presence of only a very few intact microfibrils which showed marked disorganisation within the interbeaded domains. Metabolic pulse-chase studies identified intracellularly a population of truncated proFib molecules which were secreted more slowly than the normal proFib derived from the normal allele. Culture media contained strikingly reduced amounts of wild-type proFib in comparison to fibrillin (Fib). Our findings imply that (1) the truncated proFib is secreted and disturbs microfibril assembly; (2) the mutation is probably close to a putative cleavage site in the proFib C terminus necessary for the conversion of proFib to Fib; (3) the truncated proFib is over-N-glycosylated due to intracellular retention rather than incomplete cleavage of proFib with persistence ofN-glycosylated sites; (4) not all potentialN-glycosylation sites in proFib seem to be normally used, since we could produce over-N-glycosylated proFib in normal cells by brefeldin A mediated intracellular captivation and subsequent appearance of over-glycosylated Fib in culture medium upon removal of the compound. It is conceivable that post-translational over-modification might be important for modulating the phenotype of FBN1 mutations in Marfan syndrome.

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Citation Excerpt :
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^f1: Corresponding author

^f2: Present address: M. Raghunath, Institute of Physiological Chemistry and Pathobiochemistry, Waldeyerstr. 15, D-48149 Münster, Germany.

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Journal of Molecular Biology

Regular ArticleTruncated Profibrillin of a Marfan Patient is of Apparent Similar Size as Fibrillin: Intracellular Retention Leads to over-N-glycosylation

Abstract

Regular Article
Truncated Profibrillin of a Marfan Patient is of Apparent Similar Size as Fibrillin: Intracellular Retention Leads to over-N-glycosylation