A heterozygous mutation of beta-actin associated with neutrophil dysfunction and recurrent infection.
A human disorder caused by mutation in nonmuscle actin has not been reported. We report here a variant of nonmuscle actin in a female patient with recurrent infections, photosensitivity, and mental retardation. She also had abnormalities in neutrophil chemotaxis, superoxide production, and membrane potential response. Two-dimensional PAGE analysis of proteins from neutrophils and other cell types from this patient demonstrated a unique protein spot migrating at 42 kDa with pI shifted slightly to neutral relative to normal beta- and gamma-actin. Digestion peptide mapping and Western blotting showed this spot to be an abnormal actin. A full-length cDNA library was constructed by using mRNA from patient's cells and cDNA encoding the mutant beta-actin molecule was identified by an in vitro translation method. Sequencing of the clones demonstrated a G-1174 to A substitution, predicting a glutamic acid-364 to lysine substitution in beta-actin and eliminating a HinfI DNase restriction site found in normal beta-actin sequence. By HinfI digestion and by sequencing, the mutation in one allele of patient's genomic DNA was confirmed. Though no defect in cell-free polymerization of actin was detected, this defect lies in a domain important for binding to profilin and other actin-regulatory molecules. In fact, the mutant actin bound to profilin less efficiently than normal actin did. Heterozygous expression of mutant beta-actin in neutrophils and other cells of this patient may act in a dominant-negative fashion to adversely affect cellular activities dependent on the function of nonmuscle actin.
Institute of Medical Science, University of Tokyo, Minatoku, Tokyo 108-8639, Japan. hnunoi@kaiju.medic.kumamoto-u.ac.jp
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Nunoi
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Yamazaki
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Tsuchiya
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Kato
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Malech
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Matsuda
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Kanegasaki
D000199:Actins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002633:Chemotaxis / Q000502:physiology; D002648:Child; D003001:Cloning, Molecular; D003285:Contractile Proteins; D018076:DNA, Complementary / Q000737:chemistry; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D006579:Heterozygote; D006801:Humans; D007239:Infections / Q000235:genetics* / Q000276:immunology; D008840:Microfilament Proteins / Q000378:metabolism; D009154:Mutation; D009504:Neutrophils / Q000737:chemistry / Q000502:physiology*; D012150:Polymorphism, Restriction Fragment Length; D051304:Profilins; D011485:Protein Binding; D014176:Protein Biosynthesis; D011506:Proteins / Q000032:analysis; D017421:Sequence Analysis; D013481:Superoxides / Q000378:metabolism
D000199:Actins; D003285:Contractile Proteins; D018076:DNA, Complementary; D008840:Microfilament Proteins; C495738:PFN1 protein, human; D051304:Profilins; D011506:Proteins; D013481:Superoxides