Ahmad I, Barnstable C J
Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, CT 06510.
Exp Eye Res. 1993 Jan;56(1):51-62. doi: 10.1006/exer.1993.1008.
Expression of both particulate and soluble forms of guanylate cyclase have been identified in adult rat retina using reverse transcriptase-PCR amplification of retinal RNA and sequencing of the cloned cDNAs. Over a 267-amino acid region, the retinal particulate guanylate cyclase was found to be identical in sequence to the GC-A form of the enzyme found in many tissues. No expression of the closely related GC-B or GC alpha forms of the enzyme was found. mRNA corresponding to both subunits of the soluble form of guanylate cyclase were detected in retinal. The sequence corresponding to the 70-kDa subunit was identical to that from rat lung over a 304-amino acid region and the sequence corresponding to the 82-kDa subunit showed only one amino acid difference over a 275-amino acid region. From Northern analyses the level of expression of the soluble guanylate cyclase in retina was higher than that in lung. In situ hybridization to sections of adult retina indicated that the particulate guanylate cyclase was expressed predominantly in rod photoreceptors. Although the soluble form of the enzyme was detected in all retinal layers, the level of expression was much higher in the inner nuclear layer. The results suggest that multiple enzymes and hence multiple regulatory pathways may control cGMP levels in rod photoreceptors and that cGMP may play an important role in neurons of the inner retina.
利用成年大鼠视网膜RNA的逆转录聚合酶链反应扩增和克隆cDNA测序，已在成年大鼠视网膜中鉴定出鸟苷酸环化酶的颗粒形式和可溶性形式的表达。在一个267个氨基酸的区域内，发现视网膜颗粒鸟苷酸环化酶的序列与许多组织中发现的该酶的GC-A形式相同。未发现该酶密切相关的GC-B或GCα形式的表达。在视网膜中检测到与鸟苷酸环化酶可溶性形式的两个亚基相对应的mRNA。与70 kDa亚基相对应的序列在一个304个氨基酸的区域内与大鼠肺的序列相同，与82 kDa亚基相对应的序列在一个275个氨基酸的区域内仅显示一个氨基酸差异。通过Northern分析，视网膜中可溶性鸟苷酸环化酶的表达水平高于肺。对成年视网膜切片进行原位杂交表明，颗粒鸟苷酸环化酶主要在视杆光感受器中表达。虽然在所有视网膜层中都检测到了该酶的可溶性形式，但在内核层中的表达水平要高得多。结果表明，多种酶以及多种调节途径可能控制视杆光感受器中的cGMP水平，并且cGMP可能在内视网膜神经元中起重要作用。
