Reyes-Alcaraz Arfaxad, Lee Yoo-Na, Son Gi Hoon, Kim Nam Hoon, Kim Dong-Kyu, Yun Seongsik, Kim Dong-Hoon, Hwang Jong-Ik, Seong Jae Young
Graduate School of Medicine, Korea University, Seoul 02841, Republic of Korea.
Sci Rep. 2016 Feb 24;6:21453. doi: 10.1038/srep21453.
The novel neuropeptide spexin (SPX) was discovered to activate galanin receptor 2 (GALR2) and 3 (GALR3) but not galanin receptor 1 (GALR1). Although GALR2 is known to display a function, particularly in anxiety, depression, and appetite regulation, the further determination of its function would benefit from a more stable and selective agonist that acts only at GALR2. In the present study, we developed a GALR2-specific agonist with increased stability in serum. As galanin (GAL) showed a low affinity to GALR3, the residues in SPX were replaced with those in GAL, revealing that particular mutations such as Gln5 → Asn, Met7 → Ala, Lys11 → Phe, and Ala13 → Pro significantly decreased potencies toward GALR3 but not toward GALR2. Quadruple (Qu) mutation of these residues still retained potency to GALR2 but totally abolished the potency to both GALR3 and GALR1. The first amino acid modifications or D-Asn1 substitution significantly increased the stability when they are incubated in 100% fetal bovine serum. Intracerebroventricular administration of the mutant peptide with D-Asn1 and quadruple substitution (dN1-Qu) exhibited an anxiolytic effect in mice. Taken together, the GALR2-specific agonist with increased stability can greatly help delineation of GALR2-mediated functions and be very useful for treatments of anxiety disorder.
新型神经肽鲽鱼素（SPX）被发现可激活甘丙肽受体2（GALR2）和3（GALR3），但不能激活甘丙肽受体1（GALR1）。尽管已知GALR2具有一定功能，尤其是在焦虑、抑郁和食欲调节方面，但其功能的进一步确定将受益于一种更稳定且仅作用于GALR2的选择性激动剂。在本研究中，我们开发了一种在血清中稳定性增强的GALR2特异性激动剂。由于甘丙肽（GAL）对GALR3的亲和力较低，因此将SPX中的残基替换为GAL中的残基，结果表明，特定突变如Gln5→Asn、Met7→Ala、Lys11→Phe和Ala13→Pro可显著降低对GALR3的效力，但对GALR2的效力则无影响。这些残基的四重（Qu）突变仍保留对GALR2的效力，但完全消除了对GALR3和GALR1的效力。当在100%胎牛血清中孵育时，第一个氨基酸修饰或D-Asn1取代可显著提高稳定性。脑室内注射具有D-Asn1和四重取代的突变肽（dN1-Qu）在小鼠中表现出抗焦虑作用。综上所述，稳定性增强的GALR2特异性激动剂可极大地有助于阐明GALR2介导的功能，对焦虑症的治疗非常有用。
