CAH: Calcium Channels as Therapeutic Targets

描述(由申请人提供)： 在Bob Rosenberg博士和Gerry Oxford博士的共同指导下，这款K08应用程序有两个目标：1)了解电压激活钙通道与垂体前叶调节多肽分泌偶联的细胞机制；2)评估靶向钙通道阻断对先天性肾上腺皮质增生症(CAH)的临床影响，CAH是一种由垂体高分泌引起的疾病。在对垂体促肾上腺皮质激素细胞系(ATT-20)的研究中，我发现了三种不同的高电压激活的钙通道，它们的表达丰度相似。尽管如此，只有L型[二氢吡啶(DHP)敏感]通道能够触发钙依赖的促肾上腺皮质激素分泌。因此，这项建议的主要焦点是研究DHP敏感通道与ACTH释放之间的偶联机制。我推测，L类通道的不同定位解释了促肾上腺皮质激素分泌细胞中神经分泌器的不同功能。我建议：a)用免疫细胞化学/共聚焦显微镜检查钙通道和突触成分的细胞位置，b)用显性-负性方法破坏偶联。在儿童最常见的肾上腺疾病CAH中，皮质醇产生的分子缺陷消除了对垂体前叶的正常负反馈，导致ACTH分泌增加。升高的ACTH进一步增加皮质醇前体，并将这些类固醇中间体分流到雄激素合成途径。临床上的污点(例如，成人的生殖器模糊、男性化和身材矮小)是由于雄激素过多造成的。治疗需要终生糖皮质激素替代，以恢复正常的反馈机制。然而，很难确定糖皮质激素替代的“最佳水平”：治疗不足会导致肾上腺功能不全和雄激素过剩；过度治疗会导致糖皮质激素过剩(例如肥胖、葡萄糖耐受和骨量减少)。我对培养的脑垂体细胞的研究表明，选择性地阻断L型(DHP敏感)通道，进而抑制促肾上腺皮质激素的释放，将通过允许较低的糖皮质激素剂量提供一种新的辅助治疗。这将导致增强的线性生长和改善的骨密度。这些基础研究和临床研究相辅相成，共同加强了我们对多肽分泌的细胞机制的理解。此外，它们还可以改善高分泌性条件下的治疗，如CAH。

DESCRIPTION (provided by applicant): This K08 application under the co-mentorship of Drs. Bob Rosenberg and Gerry Oxford has two goals: 1) to understand the cellular mechanisms that underlie coupling of voltage-activated calcium channels to regulated peptide secretion in the anterior pituitary, and 2) to assess the clinical impact of targeted calcium channel blockade in Congenital Adrenal Hyperplasia (CAH), a disorder resulting from pituitary hypersecretion. In studies of a pituitary corticotroph cell line (AtT-20) I identified three distinct high voltage-activated calcium channels that are expressed in similar abundance. Despite this, only the L-type [dihydropyridine (DHP)-sensitive] channel is capable of triggering calcium-dependent secretion of ACTH. The primary focus of this proposal, therefore, is to examine the mechanisms that underlie the coupling of DHP-sensitive channels to ACTH release. I hypothesize that differential localization of the L-type channels accounts for the distinct function of the neurosecretory apparatus in ACTH-secreting cells. I propose to: a) examine the cellular sites of calcium channels and synaptic components using immunocytochemistry/ confocal microscopy, and b) disrupt coupling using a dominant-negative approach. In CAH, the most common adrenal disorder in children, a molecular defect in cortisol production removes normal negative feedback to the anterior pituitary and results in elevated ACTH secretion. Elevated ACTH further increases cortisol precursors, and shunts these steroid intermediates to androgen synthetic pathways. The clinical stigmata (e.g., ambiguous genitalia, virilization and short stature in adults) are due to the excess in androgens. Treatment requires life-long glucocorticoid replacement to restore the normal feedback mechanism. Determining the "optimal level" ofglucocorticoid replacement, however, is difficult: under-treatment leads to adrenal insufficiency and androgen excess; over-treatment leads to glucocorticoid excess (e.g., obesity, glucose intolerance and osteopenia). My work with the pituitary cells in culture suggests that selective pharmacologic blockade of L-type (DHP-sensitive) channels, and, in turn, attenuation of ACTH release, will provide a novel adjunct therapy by allowing lower glucocorticoid dosing. This would result in enhanced linear growth and improved bone mineral density. These basic research and clinical studies complement one another, and together, they should enhance our understanding of the cellular mechanisms underlying peptide secretion. Furthermore, they may allow for improved treatment in hypersecretory conditions, such as CAH.