SPRY domain-containing SOCS box (SSB) protein interaction with Par-4: Structure and biochemical implications

细胞因子信号转导抑制因子(SoCs)蛋白是细胞内负性调节激素和生长因子作用的分子，其功能重要性已在许多生理研究中得到证实。SOCS盒是SOCS蛋白的一小部分，被认为有助于SOCS靶蛋白的降解。含有SPRY结构域的SoCS盒蛋白-2(SSB-2)是大SOCS家族(SSB-1至-4)的四种蛋白之一，具有一个SOCS盒和一个中心SPRY结构域。SPRY结构域调节与细胞内其他蛋白质的相互作用。已知有300多种蛋白质含有SPRY结构域。我们最近使用核磁共振(核磁共振)光谱确定了作为SSB-2的一部分的第一个SPRY结构域的原子结构。我们进一步确定PAR-4(前列腺凋亡反应-4)是SSB-1、-2和-4的新的直接蛋白结合伙伴，而不是SSB-3。随后，广泛的突变分析确定了一系列SSB-2突变体，它们不能结合PAR-4，但保留了结构完整性。癌细胞通过一系列遗传事件发展，逃避细胞程序性死亡或凋亡，继续不适当地生长。PAR-4最初被发现是一种在前列腺癌细胞凋亡过程中上调的基因，主要似乎是使癌细胞对凋亡刺激敏感。本提案旨在进一步研究SSB-PAR-4结合。将确定该复合体的3D结构，并表征这种相互作用的生化后果。如果SSB蛋白调节PAR-4水平，那么化学干扰SSB-PAR-4结合可能会导致PAR-4蛋白水平增加，使癌细胞更容易受到细胞毒药物的杀伤。

The suppressor of cytokine signalling (SOCS) proteins, are intracellular molecules that negatively regulate hormone and growth factor action, and whose functional importance has been borne out in many physiological studies. The SOCS box is a small part of the SOCS proteins that is believed to facilitate degradation of SOCS target proteins. The SPRY domain-containing SOCS box protein-2 (SSB-2) is one of four proteins within the greater SOCS family (SSB-1 to -4), which have a SOCS box and a central SPRY domain. The SPRY domain mediates interaction with other proteins within the cell. Over 300 proteins are known to contain a SPRY domain. We recently determined the first atomic structure of a SPRY domain as part of SSB-2, using nuclear magnetic resonance (NMR) spectroscopy. We further identified Par-4 (prostate apoptosis response-4) as a novel and direct protein binding partner for SSB-1, -2 and -4, but not SSB-3. Extensive mutational analysis subsequently identified a series of SSB-2 mutants that were unable to bind Par-4 but retained structural integrity. Cancer cells develop through a series of genetic events and escape programmed cell death or apoptosis, continuing to grow inappropriately. Par-4 was originally discovered as a gene up-regulated in prostate cancer cells undergoing apoptosis and primarily appears to sensitise cancer cells to apoptotic stimuli. This proposal aims to further investigate SSB-Par-4 binding. The 3D structure of the complex will be determined and biochemical consequences of this interaction characterised. If SSB proteins regulate Par-4 levels, then chemical disruption of SSB-Par-4 binding could potentially result in an increase in Par-4 protein levels, making cancer cells more susceptible to killing by cytotoxic drugs.