Identification of functional domains in sarcoglycans essential for their interaction and plasma membrane targeting

Chen, Jiwei; Shi, Wei‐Xing; Zhang, Yuguang; Sokol, Randi; Cai, Hong; Lun, Mingyue; Moore, Brian; Farber, Matthew J.; Stepanchick, Joel S.; Bönnemann, Carsten G.; Chan, Yiu-mo

doi:10.1016/j.yexcr.2006.01.024

Cited by 34 publications

(59 citation statements)

References 53 publications

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“…The N-terminal half extracellular domain is important for sarcoglycan interaction and disruption of the b/d-sarcoglycan interaction will affect membrane localization. 35 Immunofluorescence analyses in our patients further confirm these findings. Patients carrying this mutation present variable phenotypes probably due to still unknown molecular mechanisms (i.e., unrecognized polymorphisms in sarcoglycans or related proteins that modify the stability of the complex).…”

Section: Study Design and Patient Cohort All Patients Diagnosed Withsupporting

confidence: 83%

Clinical and genetic spectrum in limb-girdle muscular dystrophy type 2E

et al. 2015

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Objective: To determine the clinical spectrum of limb-girdle muscular dystrophy 2E (LGMD2E) and to investigate whether genetic or biochemical features can predict the phenotype of the disease.Methods: All LGMD2E patients followed in participating centers were included. A specific clinical protocol was created, including quantitative evaluation of motor, respiratory, and cardiac function. Phenotype was defined as severe or mild if the age at loss of ambulation occurred before or after 18 years. Molecular analysis of SGCB gene and biochemical features of muscle biopsies were reviewed.Results: Thirty-two patients were included (16 male, 16 female; age 7-67 years; 15 severe, 12 mild, and 5 unknown). Neurologic examination showed proximal muscle weakness in all patients, but distal involvement was also observed in patients with severe disease early in the disease course. Cardiac involvement was observed in 20 patients (63%) even before overt muscle involvement. Six patients had restrictive respiratory insufficiency requiring assisted ventilation (19%). Seventeen different mutations were identified, and 3 were recurrent. The c.377_384dup (13 alleles) was associated with the severe form, the c.-22_10dup (10) with the milder form, and the c.341C.T (9) with both. The entire sarcoglycan complex was undetectable by muscle immunohistochemistry or Western blot in 9/10 severe cases and reduced in 7/7 mild cases. The residual amount of sarcoglycan in muscle resulted a predictor of age at loss of ambulation.Conclusions: This study expands the spectrum of phenotype in b-sarcoglycanopathy and provides strong evidence that severity of clinical involvement may be predicted by SGCB gene mutation and sarcoglycan protein expression. Sarcoglycanopathies are recessive limb-girdle muscular dystrophies (LGMDs) and represent 20%-25% of all LGMDs and 40%-65% of LGMD cases with infantile onset.1,2 Sarcoglycanopathies are caused by mutations in genes encoding 4 transmembrane glycoproteins, a-, b-, g-, and d-sarcoglycan, that form a tetrameric complex at the cell membrane of skeletal and cardiac muscle and play an important role in stabilizing the dystrophin-associated glycoprotein complex localized in the sarcolemma of muscle fibers. [3][4][5][6][7] Mutations in individual sarcoglycan genes are responsible for LGMD2C (g-sarcoglycan, SGCC gene q12 8 ), LGMD2D (a-sarcoglycan, SGCA 9,10 ), LGMD2E (b-sarcoglycan, SGCB 11,12 ), and LGMD2F (d-sarcoglycan, SGCD 13 ).LGMD2C and 2D are the most frequent and extensively studied of the 4 sarcoglycanopathies, with a clinical phenotype characterized by progressive skeletal muscle weakness ranging from a severe Duchenne-like dystrophy to a *These authors contributed equally to this work.

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Section: Study Design and Patient Cohort All Patients Diagnosed Withsupporting

confidence: 83%

Clinical and genetic spectrum in limb-girdle muscular dystrophy type 2E

et al. 2015

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“…Rabbit polyclonal antibody specific for ␣-sarcoglycan was a generous gift from Yi-umo M. Chan (McColl-Lockwood Laboratory for Muscular Dystrophy Research, Department of Neurology, Carolinas Medical Center). 31 Mouse monoclonal antibody specific for poly-His was from Sigma. The antibody specific for ubiquitin was from BioMol International (Plymouth Meeting, PA).…”

Section: Antibodiesmentioning

confidence: 99%

“…Notably, all ␣-sarcoglycan missense mutations are mapped in the extracellular domain, a region critical for the organization of a stable sarcoglycan tetramer. 31,40 Most of the missense mutations generate polypeptides that usually are unable to fold correctly. Misfolded, or damaged proteins typically undergo degradation via the ubiquitin-proteasome system.…”

mentioning

confidence: 99%

Inhibition of Proteasome Activity Promotes the Correct Localization of Disease-Causing α-Sarcoglycan Mutants in HEK-293 Cells Constitutively Expressing β-, γ-, and δ-Sarcoglycan

Gastaldello

D'Angelo

Franzoso

et al. 2008

The American Journal of Pathology

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Sarcoglycanopathies are progressive muscle-wasting disorders caused by genetic defects of four proteins, ␣-, ␤-, ␥-, and ␦-sarcoglycan, which are elements of a key transmembrane complex of striated muscle. The proper assembly of the sarcoglycan complex represents a critical issue of sarcoglycanopathies, as several mutations severely perturb tetramer formation. Misfolded proteins are generally degraded through the cell's quality-control system; however, this can also lead to the removal of some functional polypeptides. To explore whether it is possible to rescue sarcoglycan mutants by preventing their degradation, we generated a heterologous cell system, based on human embryonic kidney (HEK) 293 cells, constitutively expressing three (␤, ␥, and ␦) of the four sarcoglycans. In these ␤␥␦-HEK cells, the lack of ␣-sarcoglycan prevented complex formation and cell surface localization, wheras the presence of ␣-sarcoglycan allowed maturation and targeting of the tetramer. As in muscles of sarcoglycanopathy patients, transfection of ␤␥␦-HEK cells with disease-causing ␣-sarcoglycan mutants led to dramatic reduction of the mutated proteins and the absence of the complex from the cell surface. Proteasomal inhibition reduced the degradation of mutants and facilitated the assembly and targeting of the sarcoglycan complex to the plasma membrane. These data provide important insights for the potential development of pharmacological therapies for sarcoglycanopathies.

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“…8C). This disruption was particularly impressive given that β-and δ-SG form a core around which the α-and γ-SG are attached [41]. Likewise, SSPN double mutant C155A + C184A also disrupted SG-SSPN complex formation in a dominant-negative fashion.…”

Section: Analysis Of Sg Binding Sites Within Sspnmentioning

confidence: 97%

“…In addition to interacting with the SGs, SSPN also interacts with β-DG through distinct protein interaction sites (Miller and Crosbie, unpublished results). The extracellular Cys-rich region of the SG proteins plays critical roles in assembly and stability of the SG subcomplex [41,43], suggesting that thiol-mediated protein interactions are important for the stability of the entire DGC. Our data suggest that the Cys residues within SSPN may also be important for stability of the DGC based on our observations that expression of two Cys→Ala SSPN mutants caused de-stablization of the tetrameric SG-subcomplex.…”

Section: Model Of Sspn-mediated Protein Interactions Within Dgcmentioning

confidence: 99%

Structural and functional analysis of the sarcoglycan–sarcospan subcomplex

Miller

Wang

Nassar

et al. 2007

Experimental Cell Research

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Sarcospan is a component of the dystrophin-glycoprotein complex that forms a tight subcomplex with the sarcoglycans. The sarcoglycan-sarcospan subcomplex functions to stabilize α-dystroglycan at the plasma membrane and perturbations of this subcomplex are associated with autosomal recessive limb-girdle muscular dystrophy. In order to characterize protein interactions within this subcomplex, we first demonstrate that sarcospan forms homo-oligomers within the membrane. Experiments with a panel of site-directed mutants reveal that proper structure of the large extracellular loop is an important determinant of oligo formation. Furthermore, the intracellular N-and C-termini contribute to stability of sarcospan-mediated webs. Point mutation of each cysteine residue reveals that Cys 162 and Cys 164 within the large extracellular loop form disulfide bridges, which are critical for proper sarcospan structure. The extracellular domain of sarcospan also forms the main binding site for the sarcoglycans. We propose a model whereby sarcospan forms homo-oligomers that cluster the components of the dystrophin-glycoprotein complex within the membrane.

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Identification of functional domains in sarcoglycans essential for their interaction and plasma membrane targeting

Cited by 34 publications

References 53 publications

Clinical and genetic spectrum in limb-girdle muscular dystrophy type 2E

Clinical and genetic spectrum in limb-girdle muscular dystrophy type 2E

Inhibition of Proteasome Activity Promotes the Correct Localization of Disease-Causing α-Sarcoglycan Mutants in HEK-293 Cells Constitutively Expressing β-, γ-, and δ-Sarcoglycan

Structural and functional analysis of the sarcoglycan–sarcospan subcomplex

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