Dysferlin expression in tubular aggregates: their possible relationship to endoplasmic reticulum stress.
Dysferlin is a newly identified sarcolemmal protein related to Miyoshi myopathy and limb-girdle muscular dystrophy. Although its function is still unknown, it is inferred from the presence of C2 domains and a transmembrane domain in its sequence that dysferlin may be expressed or located not only at the sarcolemma but also in other membranous organelles to interact with Ca(2+). Tubular aggregates (TAs) are derived from sarcoplasmic reticulum (SR) and found in various myopathies, especially in those related to disturbed intra-sarcoplasmic Ca(2+) homeostasis. To clarify the expression of dysferlin in TAs and the relationship among TA formation, dysferlin expression, and endoplasmic reticulum (ER) stress, we examined the expression of dysferlin and other sarcolemmal proteins by immunohistochemistry in 12 muscle biopsy specimens with TAs from 11 cases of periodic paralysis and 1 case of myalgia/cramps syndrome. Moreover, the expression of glucose-regulated protein 78 (GRP78) and GRP94, which are up-regulated under ER stress, was also examined by immunohistochemistry and immunoblotting. TAs showed strong expression of dysferlin. GRP78 and GRP94 were also intensely expressed in TAs. Total amounts of GRP78 and GRP94 were significantly increased in muscles with TAs compared with normal controls. These results indicate that muscles with TAs seem to be under ER stress, probably resulting from disturbed intra-sarcoplasmic Ca(2+) homeostasis. Strong expression of dysferlin in TAs suggests the possibility that it is located not only at the sarcolemma but also in the SR, at least in the pathological conditions.
Ikezoe
Koji
K
Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University 60, 812-8582, Fukuoka, Japan. kikezoe@neuro.med.kyushu-u.ac.jp
Furuya
Hirokazu
H
Ohyagi
Yasumasa
Y
Osoegawa
Manabu
M
Nishino
Ichizo
I
Nonaka
Ikuya
I
Kira
Jun-Ichi
J
D000293:Adolescent; D000328:Adult; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D003598:Cytoskeletal Proteins / Q000378:metabolism; D000073939:Dysferlin; D049030:Dystroglycans; D016189:Dystrophin / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000473:pathology; D000091342:Endoplasmic Reticulum Chaperone BiP; D005260:Female; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D007797:Laminin / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000378:metabolism / Q000473:pathology; D009124:Muscle Proteins / Q000276:immunology / Q000378:metabolism*; D020914:Myopathies, Structural, Congenital / Q000378:metabolism* / Q000473:pathology; D018013:Receptors, Neuropeptide / Q000378:metabolism; D012508:Sarcolemma / Q000378:metabolism / Q000473:pathology; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases
D003598:Cytoskeletal Proteins; C483081:DAG1 protein, human; C114839:DYSF protein, human; D000073939:Dysferlin; D016189:Dystrophin; D000091342:Endoplasmic Reticulum Chaperone BiP; C467732:GRP8 protein, human; D018840:HSP70 Heat-Shock Proteins; C000717247:HSPA5 protein, human; D007797:Laminin; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009124:Muscle Proteins; D018013:Receptors, Neuropeptide; C018551:glucose-regulated proteins; D049030:Dystroglycans; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases