RESUMO

The KRAS oncogene drives many common and highly fatal malignancies. These include pancreatic, lung, and colorectal cancer, where various activating KRAS mutations have made the development of KRAS inhibitors difficult. Here we identify the scaffold protein SH3 and multiple ankyrin repeat domain 3 (SHANK3) as a RAS interactor that binds active KRAS, including mutant forms, competes with RAF and limits oncogenic KRAS downstream signalling, maintaining mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) activity at an optimal level. SHANK3 depletion breaches this threshold, triggering MAPK/ERK signalling hyperactivation and MAPK/ERK-dependent cell death in KRAS-mutant cancers. Targeting this vulnerability through RNA interference or nanobody-mediated disruption of the SHANK3-KRAS interaction constrains tumour growth in vivo in female mice. Thus, inhibition of SHANK3-KRAS interaction represents an alternative strategy for selective killing of KRAS-mutant cancer cells through excessive signalling.

Assuntos

Sistema de Sinalização das MAP Quinases , Mutação , Proteínas do Tecido Nervoso , Proteínas Proto-Oncogênicas p21(ras) , Animais , Proteínas Proto-Oncogênicas p21(ras)/genética , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , Humanos , Camundongos , Linhagem Celular Tumoral , Feminino , Proteínas do Tecido Nervoso/metabolismo , Proteínas do Tecido Nervoso/genética , Sistema de Sinalização das MAP Quinases/genética , Morte Celular/genética , Neoplasias/genética , Neoplasias/metabolismo , Neoplasias/patologia , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Camundongos Nus , Proteínas dos Microfilamentos

RESUMO

The vast diversity of protein phosphatase 2A (PP2A) holoenzyme composition ensures its multifaceted role in the regulation of cellular growth and signal transduction. In several pathological conditions, such as cancer, PP2A is inhibited by endogenous inhibitor proteins. Several PP2A inhibitor proteins have been identified, one of which is α-endosulfine (ENSA). ENSA inhibits PP2A activity when it is phosphorylated at Ser67 by Greatwall (Gwl) kinase. The role of ENSA in PP2A inhibition is rather well characterized, but knowledge of the mechanism of inhibition is scarce. In this study, we have performed comprehensive structural characterization of ENSA, and its interaction with PP2A A- and various B56-subunit isoforms by combining NMR spectroscopy, small-angle X-ray scattering (SAXS) and interaction assays. The results clearly indicate that ENSA is an intrinsically disordered protein containing three transient α-helical structures. ENSA was observed to interact PP2A mainly via A-subunit, as the affinity with the A-subunit is significantly stronger than with any of the B56 subunits. Based on our results, it seems that ENSA follows the dock-and-coalesce mechanism in associating with PP2A A-subunit. Taken together, our results provide an essential structural and molecular framework to understanding molecular bases of ENSA-mediated PP2A inhibition, which is crucial for the development of new therapies for diseases linked to PP2A inhibition.

Assuntos

Peptídeos e Proteínas de Sinalização Intercelular/genética , Proteínas Associadas aos Microtúbulos/genética , Neoplasias/genética , Proteína Fosfatase 2/genética , Proteínas Serina-Treonina Quinases/genética , Ciclo Celular/genética , Humanos , Mitose/genética , Neoplasias/patologia , Ressonância Magnética Nuclear Biomolecular , Fosfoproteínas/genética , Fosforilação/genética , Proteína Fosfatase 2/antagonistas & inibidores , Processamento de Proteína Pós-Traducional/genética , Espalhamento a Baixo Ângulo , Transdução de Sinais/genética , Difração de Raios X

RESUMO

Protein phosphatase 2A (PP2A) activity is critical for maintaining normal physiological cellular functions. PP2A is inhibited by endogenous inhibitor proteins in several pathological conditions including cancer. A PP2A inhibitor protein, ARPP-19, has recently been connected to several human cancer types. Accordingly, the knowledge about ARPP-19-PP2A inhibition mechanism is crucial for the understanding the disease development and the therapeutic targeting of ARPP-19-PP2A. Here, we show the first structural characterization of ARPP-19, and its splice variant ARPP-16 using NMR spectroscopy, and SAXS. The results reveal that both ARPP proteins are intrinsically disordered but contain transient secondary structure elements. The interaction mechanism of ARPP-16/19 with PP2A was investigated using microscale thermophoresis and NMR spectroscopy. Our results suggest that ARPP-PP2A A-subunit interaction is mediated by linear motif and has modest affinity whereas, the interaction of ARPPs with B56-subunit is weak and transient. Like many IDPs, ARPPs are promiscuous binders that transiently interact with PP2A A- and B56 subunits using multiple interaction motifs. In summary, our results provide a good starting point for future studies and development of therapeutics that block ARPP-PP2A interactions.