Anastasi Giuseppe, Cutroneo Giuseppina, Sidoti Antonina, Santoro Giuseppe, D'Angelo Rosalia, Rizzo Giuseppina, Rinaldi Carmen, Giacobbe Oddone, Bramanti Placido, Navarra Giuseppe, Amato Aldo, Favaloro Angelo
Dipartimento di Biomorfologia e Biotecnologie, Policlinico Universitario, Università degli Studi di Messina, Torre Biologica, Italy.
Int J Mol Med. 2005 Sep;16(3):367-74.
The sarcoglycans are transmembrane components of the dystrophin-glycoprotein complex, which links the cytoskeleton to the extracellular matrix in adult muscle fibers. Sarcoglycans seem to be functionally and pathologically as important as dystrophin. In the skeletal and cardiac muscle, the sarcoglycan subcomplex is a heterotetrameric unit composed of the transmembrane glycoproteins alpha-, beta-, gamma- and delta-sarcoglycan. A fifth sarcoglycan with significant homology to alpha-sarcoglycan, epsilon-sarcoglycan, has been identified; this sarcoglycan is expressed in both muscle and non-muscle cells. It is hypothesized that epsilon-sarcoglycan might replace alpha-sarcoglycan in smooth muscle, forming a novel sarcoglycan subcomplex consisting of epsilon-, beta-, gamma-, and delta-sarcoglycan. Recently, zeta-sarcoglycan, a novel sarcoglycan highly related to gamma-sarcoglycan and delta-sarcoglycan, has been identified. On this basis, growing evidence suggests that there are two types of sarcoglycan complex; one, in skeletal and cardiac muscle, consisting of alpha-, beta-, gamma- and delta-sarcoglycan; and the other, in smooth muscle, containing beta-, delta-, zeta- and epsilon-sarcoglycan. epsilon-sarcoglycan may be substituted for alpha-sarcoglycan in a subset of striated muscle complexes. Our results, obtained with immunofluorescence semi-quantitative analysis and molecular methods on smooth muscle biopsies of human adult gastroenteric tract, show for the first time that alpha-sarcoglycan fluorescence is also always detectable in smooth muscle, although its staining pattern is lower than epsilon-sarcoglycan. Normal alpha-sarcoglycan staining was detected at times, whereas there was reduced, but clearly detectable staining for epsilon-sarcoglycan. Moreover, gamma-sarcoglycan staining is always detectable in all analyzed biopsies. On the basis of our results, we would be able to hypothesize the existence of a pentameric or, considering zeta-sarcolgycan, a hexameric arrangement of the sarcoglycan subcomplex. The hexameric sarcoglycan subcomplex, in conformity with a larger or lower expression of single sarcoglycans, could characterize skeletal, cardiac or smooth muscle, or distinct parts of gastroenteric tract. It is intriguing to integrate these results with other vascular and urogenital smooth muscle, skeletal and cardiac muscle, while also analyzing zeta-sarcoglycan.
肌聚糖是肌营养不良蛋白 - 糖蛋白复合体的跨膜成分，该复合体在成年肌纤维中将细胞骨架与细胞外基质相连。肌聚糖在功能和病理方面似乎与肌营养不良蛋白同样重要。在骨骼肌和心肌中，肌聚糖亚复合体是一个由跨膜糖蛋白α - 、β - 、γ - 和δ - 肌聚糖组成的异四聚体单元。已鉴定出与α - 肌聚糖具有显著同源性的第五种肌聚糖，即ε - 肌聚糖；这种肌聚糖在肌肉和非肌肉细胞中均有表达。据推测，ε - 肌聚糖可能在平滑肌中替代α - 肌聚糖，形成一个由ε - 、β - 、γ - 和δ - 肌聚糖组成的新型肌聚糖亚复合体。最近，已鉴定出一种与γ - 肌聚糖和δ - 肌聚糖高度相关的新型肌聚糖，即ζ - 肌聚糖。在此基础上，越来越多的证据表明存在两种类型的肌聚糖复合体；一种存在于骨骼肌和心肌中，由α - 、β - 、γ - 和δ - 肌聚糖组成；另一种存在于平滑肌中，包含β - 、δ - 、ζ - 和ε - 肌聚糖。ε - 肌聚糖可能在一部分横纹肌复合体中替代α - 肌聚糖。我们通过对人类成人胃肠道平滑肌活检样本进行免疫荧光半定量分析和分子方法获得的结果首次表明，尽管α - 肌聚糖的染色模式低于ε - 肌聚糖，但在平滑肌中始终可检测到α - 肌聚糖荧光。有时可检测到正常的α - 肌聚糖染色，而ε - 肌聚糖的染色减少，但仍清晰可检测到。此外，在所有分析的活检样本中始终可检测到γ - 肌聚糖染色。基于我们的结果，我们能够推测肌聚糖亚复合体存在五聚体形式，或者考虑到ζ - 肌聚糖，存在六聚体形式。这种六聚体肌聚糖亚复合体，根据单个肌聚糖表达量的或多或少，可能是骨骼肌、心肌或平滑肌，或胃肠道不同部位的特征。将这些结果与其他血管和泌尿生殖系统平滑肌、骨骼肌和心肌的结果相结合，同时分析ζ - 肌聚糖，是很有趣的。
