• BMB Reports
• /
• v.34 no.5
• /
• pp.484-488
• /
• 2001

STATs are proteins with a dual function: signal transducers in the cytoplasm and transcriptional activators in the nucleus. Among the six known major STATs (STAT1-6), STAT3 has been implicated in the widest range of signaling pathways that regulate cell growth and differentiation. As a part of our on-going investigation on the pleiotropic functions of STAT proteins, we examined the role of STAT3 as a molecular adaptor that links diverse cell growth signaling pathways. We observed that STAT3 can be specifically activated by multiple cytokines, such as IL-3, in transformed fibroblasts and IL-4 or IFN-$\gamma$ in primary immune cells, respectively. The selective activation of STAT3 in H-ras-transformed NIH3T3 cells is associated with an increased expression of phosphoserioe STAT3 in these cells, compared to the parental cells. Notably phosphoresine-STAT3 interacts with oncogenic ras, shown by immunoprecipitation and Western blots. The results suggest the role of STAT3 in rasinduced cellular transformation as a molecular adaptor linking the Jak/STAT and Ras/MAPK pathways. In primary immune cells, IL-4 and IFN-$\gamma$ each induced (in addition to the characteristic STAT6 and STAT1 homodimers) the formation of STAT3-containing complexes that bind to GAS probes, which correspond to the $Fe{\varepsilon}$ Rll and $Fe{\gamma}$ RI promoter sequences, respectively. Since IL-4 and IFN-$\gamma$ are known to counter-regulate the expression of these genes, the ability of STAT3 to form heterodimeric complexes with STAT6 or STAT1 implies its role in the fine-tuned control of genes that are regulated by IL-4 and IFN-$\gamma$.

• Biomedical Science Letters
• /
• v.9 no.2
• /
• pp.105-110
• /
• 2003

Ankyrins are a ubiquitously expressed family of intracellular adaptor proteins involved in targeting diverse proteins to specialized membrane domains in both the plasma membrane and the endoplasmic reticulum. Canonical ankyrins are 190-220 kDa proteins expressed in most tissues and cell types and comprise a membrane-binding domain (MBD) of 24 ANK repeats, a spectrin-binding domain, a death domain and a C-terminal domain. Rescue studies with ankyrin-B/G chimeras have identified the C-terminal domain of ankyrin-B as the defining domain in specifying ankyrin-B activity, but the function of C-terminal domain of ankyrin-B is, however, not known. We report here that the C-terminal domain of ankyrin-B is capable of interacting with the C-terminal Region of Hsp40. The Hsps are induced not only by heat shock but also by various other environmental stresses. Hsps are also expressed constitutively at normal growth temperatures and have basic and indispensable functions in the life cycle of proteins as molecular chaperones, as well as playing a role in protecting cells from the deleterious stresses. The binding sites required in the interaction between C-terminal domain of ankyrin-B and C-terminal region of Hsp40 were characterized using the yeast two-hybrid system and GST-pull down assay. The interaction between ankyrin-B and Hsp40 represents the first direct evidence of ankyrin's role as chaperones.

• Molecules and Cells
• /
• v.41 no.1
• /
• pp.18-26
• /
• 2018

Mitochondrial quality control systems are essential for the maintenance of functional mitochondria. At the organelle level, they include mitochondrial biogenesis, fusion and fission, to compensate for mitochondrial function, and mitophagy, for degrading damaged mitochondria. Specifically, in mitophagy, the target mitochondria are recognized by the autophagosomes and delivered to the lysosome for degradation. In this review, we describe the mechanisms of mitophagy and the factors that play an important role in this process. In particular, we focus on the roles of mitophagy adapters and receptors in the recognition of damaged mitochondria by autophagosomes. In addition, we also address a functional association of mitophagy with mitochondrial dynamics through the interaction of mitophagy adaptor and receptor proteins with mitochondrial fusion and fission proteins.

• BMB Reports
• /
• v.49 no.8
• /
• pp.424-430
• /
• 2016

Autophagy, an evolutionarily conserved cellular degradation pathway of the lysosome, is associated with many physiological and pathological processes. The hallmark of autophagy is the formation of the autophagosome that engulfs and degrades cytosolic components via its fusion with the lysosome, in either a selective or a non-selective manner. Autophagy is tightly regulated by proteins encoded by autophagy-related (atg) genes. Among these proteins, ATG8/LC3 is essential for autophagosome biogenesis/maturation and it also functions as an adaptor protein for selective autophagy. In mammalian cells, several homologs of yeast Atg8 such as MAP1LC3, GABARAP, and GABARAPL 1/2 have been identified. However, the biological relevance of this gene diversity in higher eukaryotes, and their specific roles, are largely unknown. In this review, we describe the mammalian ATG8/LC3 family and discuss recent advancements in understanding their roles in the autophagic process.

• International Journal of Oral Biology
• /
• v.33 no.2
• /
• pp.71-76
• /
• 2008

The neurotrophin plays an important role in the development, differentiation and survival of the nervous system in vertebrates. It exerts its cellular effects through two different receptors, the Trk receptor tyrosine kinase neurotrophin receptor and the p75 neurotrophin receptor, a member of the tumor necrosis factor receptor superfamily. Trk and p75 neurotrophin receptors utilize specific target proteins to transmit signals into the cell. An ankyrin-rich membrane spanning protein (ARMS) was identified as a new p75 interacting protein and serves as a novel downstream target of p75 neurotrophin receptor. We sought to delineate the interaction between p75 and ARMS by deletion constructs of p75 and green fluorescent protein (GFP)-tagged ARMS. We examined the interaction between these two proteins after overexpressing them in HEK-293 cells. Using both Western blot analysis and immunocytochemistry followed by confocal laser scanning microscopy, we found out that the intracellular domain of the p75 neurotrophin receptor was important for the interaction with ARMS. The results from this study suggest that ARMS may play an important role for mediating the signals from p75 neurotrophin receptor into the cell.

• International Journal of Oral Biology
• /
• v.47 no.3
• /
• pp.33-40
• /
• 2022

Store-operated Ca²⁺ entry (SOCE) represents one of the major Ca²⁺ entry routes in non-excitable cells. It is involved in a variety of fundamental biological processes and the maintenance of Ca²⁺ homeostasis. The Ca²⁺ release-activated Ca²⁺ (CRAC) channel consists of stromal interaction molecule and Orai; however, the role and action of Homer proteins as an adaptor protein to SOCE-mediated Ca²⁺ signaling through the activation of CRAC channels in non-excitable cells still remain unknown. In the present study, we investigated the role of Homer2 in the process of Ca²⁺ signaling induced by the interaction between CRACs and Homer2 proteins in non-excitable cells. The response to Ca²⁺ entry by thapsigargin-mediated Ca²⁺ store depletion remarkably decreased in pancreatic acinar cells of Homer2^-/- mice, as compared to wild-type cells. It also showed critical differences in regulated patterns by the specific blockers of SOCE in pancreatic acinar cells of Homer2^-/- mice. The response to Ca²⁺ entry by the depletion in Ca²⁺ store markedly increased in the cellular overexpression of Orai1 and STIM1 as compared to the overexpression of Homer2 in cells; however, this response was remarkably inhibited by the overexpression of Orai1, STIM1, and Homer2. These results suggest that Homer2 has a critical role in the regulatory action of SOCE activity and the interactions between CRAC channels.

• Journal of Microbiology and Biotechnology
• /
• v.10 no.4
• /
• pp.544-546
• /
• 2000

Grb2 is an important adaptor protein in the mitogenic Ras signaling pathway of receptor tyrosine kinases, and contains one SH2 domain and two SH3 domains. The SH2 domain binds to specific phosphotyrosine motifs on receptors or adaptor proteins such as Shc. The SH2 domain antagonists may lead to blocking of the oncogenic Ras signals and to developing new antitumor agents. In the course of screening SH2 antagonists from natural sources, cslerotiorin (1) and isochromophilone IV (2) were isolated from a strain, Penicillium multicolor F1753, and their structures were established by NMR spectral data. The metabolites significantly inhibited the binding between the Grb2-SH2 domain and phosphopeptide derived from the Shc protein, with $IC_{50}$ values of $22{\;}\mu\textrm{M}{\;}and{\;}48{\;}\mu\textrm{M}$ for (1) and (2), respectively. The compounds are the first nonpeptidic inhibitors of the SH2 domain from a natural source.

• Journal of Life Science
• /
• v.18 no.8
• /
• pp.1059-1065
• /
• 2008

KIF21A is a member of the Kinesin superfamily proteins (KIFs), which are microtubule-dependent molecular motors, anterograde axonal transporters of cargoes. Recently, congenital fibrosis of the extraocular muscles 1 (CFEOM1) has been shown to result from a small number of recurrent heterozygous missense mutations of KIF21A. CFEOM1 results from the inability of mutated KIF21A to successfully deliver cargoes to the development of the occulo-motor neuron or neuromuscular junction. Here, we used an yeast two-hybrid system to identify a protein that interacts with the WD-40 repeat domain of KIF21A and found a specific interaction with Purkinje cell protein-2 (Pcp-2), a small protein also known as L7. Pcp-2 protein bound to the WD-40 domain of KIF21A and KIF21B but not to other KIFs in yeast two-hybrid assays. In addition, this specific interaction was also observed in the glutathione S-transferase pull-down assay. An antibody to Pcp-2 specifically co-immunoprecipitated KIF21A associated with Pcp-2 from mouse brain extracts. These results suggest that Pcp-2 may be involved in the KIF21A-mediated transport as a KIF21A adaptor protein.

• The Korean Journal of Physiology and Pharmacology
• /
• v.8 no.3
• /
• pp.167-172
• /
• 2004

The kinesin proteins (KIFs) make up a large superfamily of molecular motors that transport cargo such as vesicles, protein complexes, and organelles. KIF5 is a heterotetrameric motor that conveys vesicles and plays an important role in neuronal function. Here, we used the yeast two-hybrid system to identify the neuronal protein(s) that interacts with the tail region of KIF5 and found a specific interaction with ${\beta}III$ spectrin. The amino acid residues between 1394 and 1774 of ${\beta}III$ spectrin were required for the interaction with KIF5C. ${\beta}III$ spectrin also bound to the tail region of neuronal KIF5A and ubiquitous KIF5B but not to other kinesin family members in the yeast two-hybrid assay. In addition, these proteins showed specific interactions, confirmed by GST pull-down assay and co-immunoprecipitation. ${\beta}III$ spectrin interacted with GST-KIF5 fusion proteins, but not with GST alone. An antibody to ${\beta}III$ spectrin specifically co-immunoprecipitated KIF5s associated with ${\beta}III$ spectrin from mouse brain extracts. These results suggest that KTF5 motor proteins transport vesicles or organelles that are coated with ${\beta}III$ spectrin.

• Biomedical Science Letters
• /
• v.9 no.3
• /
• pp.159-165
• /
• 2003

Ankyrins are a ubiquitously expressed family of intracellular adaptor proteins involved in targeting diverse proteins to specialized membrane domains in both the plasma membrane and the endoplasmic reticulum. Recently, the studies with C-terminus of ankyrins have identified that ankyrin-B is capable of interacting with Hsp40 and sAnkl is capable of interacting with obscurin and titin, but the function of C-terminal domain of ankyrin-G remains unknown. To identify proteins interacting C-terminus of ankyrin-G, we used the C-terminus of ankyrin-G as a bait for a yeast two-hybrid screen of brain cDNA library. Approximately 1.33$\times$l0$^6$ transformants were screened, of which 13 positive clones were obtained as determined by activation of HIS3, ADE2 and MELl reporter genes. Sequence analyses of these 13 plasmids revealed that cDNA inserts of 13 colonies showed highly homologous to 11 genes, including 5 known (i.e., Na$^+$/K$^+$ ATPase $\beta$1, SERBPl, UTF2, cytochrome C oxidase and collagen IV $\alpha$2) and 6 unknown genes. The evaluation of the proteins that emerge from these experiments provides a rational approach to investigate the those proteins significant in interaction with ankyrin-G.