Division of Urology, Veterans Affairs Boston Healthcare System, Boston, MA 02132, USA.
BJU Int. 2012 Dec;110(11 Pt C):E1163-72. doi: 10.1111/j.1464-410X.2012.11410.x. Epub 2012 Aug 16.
What's known on the subject? and What does the study add? Caveolae are specialised regions of bladder smooth muscle (BSM) cell membranes where specific signalling pathways are regulated. Caveolin proteins are involved in caveolar biogenesis and function as signal transduction regulators. Expression of caveolin-1, -2, and -3 has been previously identified in the bladder; however, the distribution and relative expression of these proteins have not been defined. The present data show significant differences in the spatial distribution of caveolin proteins throughout the bladder wall. Region dependent variations in the co-localisation of caveolin subtypes in detrusor SM were also detected. These findings support the premise that the unique spatial pattern of caveolin proteins associated with BSM cells may enable regionally distinct functional responses to common stimuli.
• To determine the regional expression profile of caveolin isoforms (integral membrane proteins abundant in caveolae), the spatial relationships among caveolin proteins within specific smooth muscle (SM) regions and the extent of their molecular interactions in bladder SM (BSM).
• Regional differences in the expression of caveolin family members were determined by quantitative reverse transcriptase-polymerase chain reaction and Western blot of RNA and protein extracted from the base, body and dome of rat bladders. • To evaluate the distribution of caveolin-1 (Cav-1), Cav-2 and Cav-3 within the bladder, longitudinal tissue sections from the base to dome were processed for confocal microscopy and quantified for intensity of immunoreactivity (IR) and extent of co-localisation. • Interactions among Cav-1, Cav-2 and Cav-3 were determined by co-immunoprecipitation.
• Differential expression of Cav-1 and Cav-3 was detected among bladder regions, with lowest expression in the bladder base relative to the dome. • Cav-1 was highly expressed in all regions, although an increase in IR from submucosa to serosa was detected in each region. • The distribution of Cav-2 IR generally paralleled Cav-1, but progressively decreased from submucosa to serosa in each region. • Cav-3 expression predominated in the medial region of BSM increasing progressively from base to dome, but was poorly expressed in the outer SM layer particularly in the dome. • Cav-1 co-precipitated extensively with both Cav-2 and Cav-3. Co-precipitation between Cav-3 and Cav-2 was also detected.
• The isoform-specific spatial distribution and distinct molecular interactions among caveolins in BSM may contribute to the contractile heterogeneity of BSM cells and facilitate differential modulation of responses to local stimuli. • As BSM caveolae regulate key signalling processes involved in contraction, altered expression of caveolin proteins may generate a regional imbalance in contraction/relaxation responses, thus leading to bladder dysfunction.
确定 caveolin 异构体（富含 caveolae 的完整膜蛋白）在膀胱平滑肌 (BSM) 中的区域表达谱。
确定特定平滑肌 (SM) 区域内 caveolin 蛋白之间的空间关系及其在 BSM 中的分子相互作用程度。
通过定量逆转录聚合酶链反应 (qRT-PCR) 和从大鼠膀胱基部、体部和顶部提取的 RNA 和蛋白质的 Western blot 确定 caveolin 家族成员的区域差异。
为了评估 caveolin-1 (Cav-1)、Cav-2 和 Cav-3 在膀胱中的分布，对从基部到顶部的膀胱纵行组织切片进行共聚焦显微镜处理，并对免疫反应性 (IR) 强度和共定位程度进行量化。
通过共免疫沉淀确定 Cav-1、Cav-2 和 Cav-3 之间的相互作用。
在膀胱区域之间检测到 Cav-1 和 Cav-3 的差异表达，相对于顶部，膀胱基部的表达最低。
Cav-1 在所有区域都高度表达，尽管在每个区域中从粘膜下层到浆膜层都检测到 IR 增加。
Cav-2 IR 的分布通常与 Cav-1 平行，但在每个区域中从粘膜下层到浆膜层逐渐减少。
Cav-3 表达主要在 BSM 的中间区域增加，从基部到顶部逐渐增加，但在外部 SM 层中表达较差，特别是在顶部。
Cav-1 与 Cav-2 和 Cav-3 广泛共沉淀。还检测到 Cav-3 和 Cav-2 之间的共沉淀。
BSM 中 caveolins 的同工型特异性空间分布和独特的分子相互作用可能有助于 BSM 细胞的收缩异质性，并促进对局部刺激的反应的差异调节。
由于 BSM caveolae 调节参与收缩的关键信号过程，因此 caveolin 蛋白的表达改变可能导致收缩/松弛反应的区域失衡，从而导致膀胱功能障碍。
