Zhang Houbin, Hosier Suzanne, Terew Jennifer M, Zhang Kai, Cote Rick H, Baehr Wolfgang
Methods Enzymol. 2005;403:42-56. doi: 10.1016/S0076-6879(05)03005-3.
A 17-kDa prenyl-binding protein, PrBP(PDEdelta), is highly conserved among various species from human to Caenorhabditis elegans. First identified as a putative regulatory delta subunit of the cyclic nucleotide phosphodiesterase (PDE6) purified from mammalian photoreceptor cells, PrBP(PDEdelta) has been hypothesized to reduce activation of PDE6 by the heterotrimeric G-protein, transducin, thereby desensitizing the photoresponse. However, recent work shows that PrBP(PDEdelta) interacts with numerous prenylated proteins at their farnesylated or geranylgeranylated C-termini, as well as with non-prenylated proteins. These polypeptides include small GTPases such as Rab13, Ras, Rap, and Rho6, as well as components involved in phototransduction (e.g., rod and cone PDE6, rod and cone opsin kinases). Expression of PrBP(PDEdelta) in tissues and organisms not expressing PDE6, the demonstration of multiple interacting partners with PrBP(PDEdelta), and its low abundance in rod outer segments all argue against it being a regulatory PDE6 subunit. This raises intriguing questions as to its physiological functions. In this chapter, we review the current status of PrBP(PDEdelta) and describe some of the assays used to determine these interactions in detail. In mammalian photoreceptors, the results are consistent with a role of PrBP(PDEdelta) in the transport of prenylated proteins from their site of synthesis in the inner segment to the outer segment where phototransduction occurs.
一种17千道尔顿的异戊二烯结合蛋白，即PrBP（PDEδ），在从人类到秀丽隐杆线虫的各种物种中高度保守。PrBP（PDEδ）最初被鉴定为从哺乳动物光感受器细胞中纯化出的环核苷酸磷酸二酯酶（PDE6）的假定调节性δ亚基，据推测它可通过异源三聚体G蛋白转导素减少PDE6的激活，从而使光反应脱敏。然而，最近的研究表明，PrBP（PDEδ）在其法尼基化或香叶基香叶基化的C末端与众多异戊二烯化蛋白相互作用，同时也与非异戊二烯化蛋白相互作用。这些多肽包括小GTP酶，如Rab13、Ras、Rap和Rho6，以及参与光转导的成分（如视杆和视锥PDE6、视杆和视锥视蛋白激酶）。PrBP（PDEδ）在不表达PDE6的组织和生物体中的表达、与PrBP（PDEδ）的多个相互作用伙伴的证明以及其在视杆外段中的低丰度，均表明它并非调节性PDE6亚基。这就引发了关于其生理功能的有趣问题。在本章中，我们回顾了PrBP（PDEδ）的当前研究状况，并详细描述了一些用于确定这些相互作用的检测方法。在哺乳动物光感受器中，结果表明PrBP（PDEδ）在将异戊二烯化蛋白从其在内段的合成位点运输到发生光转导的外段中发挥作用。
