Caveolin-3 T78M and T78K missense mutations lead to different phenotypes in vivo and in vitro.
Caveolins are the principal protein components of caveolae, invaginations of the plasma membrane involved in cell signaling and trafficking. Caveolin-3 (Cav-3) is the muscle-specific isoform of the caveolin family and mutations in the CAV3 gene lead to a large group of neuromuscular disorders. In unrelated patients, we identified two distinct CAV3 mutations involving the same codon 78. Patient 1, affected by dilated cardiomyopathy and limb girdle muscular dystrophy (LGMD)-1C, shows an autosomal recessive mutation converting threonine to methionine (T78M). Patient 2, affected by isolated familiar hyperCKemia, shows an autosomal dominant mutation converting threonine to lysine (T78K). Cav-3 wild type (WT) and Cav-3 mutations were transiently transfected into Cos-7 cells. Cav-3 WT and Cav-3 T78M mutant localized at the plasma membrane, whereas Cav-3 T78K was retained in a perinuclear compartment. Cav-3 T78K expression was decreased by 87% when compared with Cav-3 WT, whereas Cav-3 T78M protein levels were unchanged. To evaluate whether Cav-3 T78K and Cav-3 T78M mutants behaved with a dominant negative pattern, Cos-7 cells were cotransfected with green fluorescent protein (GFP)-Cav-3 WT in combination with either mutant or WT Cav-3. When cotransfected with Cav-3 WT or Cav-3 T78M, GFP-Cav-3 WT was localized at the plasma membrane, as expected. However, when cotransfected with Cav-3 T78K, GFP-Cav-3 WT was retained in a perinuclear compartment, and its protein levels were reduced by 60%, suggesting a dominant negative action. Accordingly, Cav-3 protein levels in muscles from a biopsy of patient 2 (T78K mutation) were reduced by 80%. In conclusion, CAV3 T78M and T78K mutations lead to distinct disorders showing different clinical features and inheritance, and displaying distinct phenotypes in vitro.
Traverso
Monica
M
Muscular and Neurodegenerative Disease Unit, University of Genoa and G. Gaslini Paediatric Institute, Genoa, Italy.
Gazzerro
Elisabetta
E
Assereto
Stefania
S
Sotgia
Federica
F
Biancheri
Roberta
R
Stringara
Silvia
S
Giberti
Laura
L
Pedemonte
Marina
M
Wang
Xiabo
X
Scapolan
Sara
S
Pasquini
Elisabetta
E
Donati
Maria A
MA
Zara
Federico
F
Lisanti
Michael P
MP
Bruno
Claudio
C
Minetti
Carlo
C
D000328:Adult; D000483:Alleles; D019943:Amino Acid Substitution; D000818:Animals; D019556:COS Cells; D002311:Cardiomyopathy, Dilated / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051244:Caveolin 3 / Q000235:genetics* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D003062:Codon; D004247:DNA / Q000032:analysis / Q000235:genetics; D004576:Electromyography; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D005799:Genes, Dominant; D005808:Genes, Recessive; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006651:Histocytochemistry; D006720:Homozygote; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008239:Lysine / Q000378:metabolism; D008297:Male; D008715:Methionine / Q000378:metabolism; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism / Q000601:surgery; D009130:Muscle, Smooth / Q000378:metabolism; D009136:Muscular Dystrophies / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020125:Mutation, Missense; D009206:Myocardium / Q000378:metabolism; D010641:Phenotype; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D051244:Caveolin 3; D003062:Codon; D020033:Protein Isoforms; D049452:Green Fluorescent Proteins; D004247:DNA; D008715:Methionine; D008239:Lysine