The interaction between calcineurin and α-synuclein is regulated by calcium and calmodulin.

Calcineurin (CN) is a protein phosphatase and widely distributed in eukaryotes, with an extremely high level of expression in mammalian brain. Alpha-synuclein (α-syn) is a small soluble protein expressed primarily at presynaptic terminals in the central nervous system. In our present study, we explored the interactions between CN and α-syn in vitro. Based on the data from microscale thermophoresis, GST pull-down assays, and co-immunoprecipitation, we found that CN binds α-syn. Furthermore, this interaction is mediated by calcium/calmodulin (Ca2+/CaM) signaling. Additionally, thapsigargin (TG) triggered an increase in CN activity and α-syn aggregation in HEK293 cells stably transfected with α-syn. Our previous study in vivo suggest that overexpression of α-syn in transgenic mice significantly promoted CN activity and subsequent nuclear translocation of nuclear factor of activated T-cells (NFAT) in the midbrain dopaminergic (mDA) neurons. These in vivo and in vitro studies have been complementary with each other, representing the changes in the CN-dependent pathway affected by overexpression of α-syn.

Model System-Guided Protein Interaction Mapping for Virus Isolated from Phloem Tissue.

Phloem localization of plant viruses is advantageous for acquisition by sap-sucking vectors but hampers host-virus protein interaction studies. In this study, Potato leafroll virus (PLRV)-host protein complexes were isolated from systemically infected potato, a natural host of the virus. Comparing two different co-immunoprecipitation (co-IP) support matrices coupled to mass spectrometry (MS), we identified 44 potato proteins and one viral protein (P1) specifically associated with virus isolated from infected phloem. An additional 142 proteins interact in complex with virus at varying degrees of confidence. Greater than 80% of these proteins were previously found to form high confidence interactions with PLRV isolated from the model host Nicotiana benthamiana. Bioinformatics revealed that these proteins are enriched for functions related to plasmodesmata, organelle membrane transport, translation, and mRNA processing. Our results show that model system proteomics experiments are extremely valuable for understanding protein interactions regulating infection in recalcitrant pathogens such as phloem-limited viruses.

All 17 S-locus F-box proteins of the S2 - and S3 -haplotypes of Petunia inflata are assembled into similar SCF complexes with a specific function in self-incompatibility.

The collaborative non-self-recognition model for S-RNase-based self-incompatibility predicts that multiple S-locus F-box proteins (SLFs) produced by pollen of a given S-haplotype collectively mediate ubiquitination and degradation of all non-self S-RNases, but not self S-RNases, in the pollen tube, thereby resulting in cross-compatible pollination but self-incompatible pollination. We had previously used pollen extracts containing GFP-fused S2 -SLF1 (SLF1 with an S2 -haplotype) of Petunia inflata for co-immunoprecipitation (Co-IP) and mass spectrometry (MS), and identified PiCUL1-P (a pollen-specific Cullin1), PiSSK1 (a pollen-specific Skp1-like protein) and PiRBX1 (a conventional Rbx1) as components of the SCF(S) (2-) (SLF) (1) complex. Using pollen extracts containing PiSSK1:FLAG:GFP for Co-IP/MS, we identified two additional SLFs (SLF4 and SLF13) that were assembled into SCF(SLF) complexes. As 17 SLF genes (SLF1 to SLF17) have been identified in S2 and S3 pollen, here we examined whether all 17 SLFs are assembled into similar complexes and, if so, whether these complexes are unique to SLFs. We modified the previous Co-IP/MS procedure, including the addition of style extracts from four different S-genotypes to pollen extracts containing PiSSK1:FLAG:GFP, to perform four separate experiments. The results taken together show that all 17 SLFs and an SLF-like protein, SLFLike1 (encoded by an S-locus-linked gene), co-immunoprecipitated with PiSSK1:FLAG:GFP. Moreover, of the 179 other F-box proteins predicted by S2 and S3 pollen transcriptomes, only a pair with 94.9% identity and another pair with 99.7% identity co-immunoprecipitated with PiSSK1:FLAG:GFP. These results suggest that SCF(SLF) complexes have evolved specifically to function in self-incompatibility.

The preclinical evaluation of the dual mTORC1/2 inhibitor INK-128 as a potential anti-colorectal cancer agent.

The colorectal cancer is the leading contributor of cancer-related mortality. Mammalian target of rapamycin (mTOR), existing in 2 complexes (mTORC1/2), is frequently dysregulated and constitutively activated in colorectal cancers. It represents an important drug target. Here we found that INK-128, the novel ATP-competitive kinase inhibitor of mTOR, blocked both mTORC1 and mTORC2 activation in colorectal cancer cells (both primary and transformed cells). The immunoprecipitation results showed that the assembly of mTORC1 (mTOR-Raptor association) and mTORC2 (mTOR-Rictor-Sin1 association) was also disrupted by INK-128. INK-128 inhibited colorectal cancer cell growth and survival, and induced both apoptotic and non-apoptotic cancer cell death. Further, INK-128 showed no effect on Erk/MAPK activation, while MEK/Erk inhibition by MEK-162 enhanced INK-128-induced cytotoxicity in colorectal cancer cells. Meanwhile, INK-128 downregulated Fascin1 (FSCN1)/E-Cadherin expressions and inhibited HT-29 cell in vitro migration. In vivo, daily INK-128 oral administration inhibited HT-29 xenograft growth in mice, which was further enhanced by MEK-162 administration. Finally, we found that INK-128 sensitized 5-fluorouracil-(5-FU)-mediated anti-HT-29 activity in vivo and in vitro. Thus, our preclinical studies strongly suggest that INK-128 might be investigated for colorectal cancer treatment in clinical trials.

Divergent evolution of potato immune receptor CC domain interactions with the Ran GTPase-activating protein 2.

Effector-triggered immunity mediated by immune receptors in plants provides powerful defense against specific pathogens. Solanum tuberosum Ran GTPase-Activating Protein 2 (StRanGAP2) interacts with immune receptors Rx and Gpa2 through their coiled-coil (CC) domains. We assayed additional CC domains from other Solanaceous immune receptors and observed interaction by co-immunoprecipitation between StRanGAP2 and a novel immune receptor, STR5. A CC domain very similar to Rx and Gpa2, STR4, failed to interact, likely due to sequence divergence in the region implicated in StRanGAP2 binding. Like Rx and Gpa2, STR5 interacted with the StRanGAP2 N-terminal WPP domain. Our findings substantiate the importance of RanGAPs as common CC-interacting proteins of multiple immune receptors requiring further study to define their roles in pathogen perception.