REFERENCE TO A SEQUENCE LISTING SUBMITTED VIA EFS-WEB

The content of the ASCII text file of the sequence listing named “18931-17_2020-01-22_Sequence-Listing_ST25,” which is 2.01 kb in size, was created on Jan. 22, 2020 and electronically submitted via EFS-Web herewith the application is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a composition for muscle enhancement comprising UNE-L domain of leucyl-tRNA synthetase as an active ingredient.

2. Description of the Related Art

Muscle is the most constituent tissue in the human body. A proper amount of muscle is needed to maintain the human body's functional capabilities and to prevent metabolic diseases. The size of muscle is regulated by intracellular signaling processes that induce anabolism or catabolism in muscle. When the signaling reactions that induce the synthesis of muscle proteins occur more than the signaling reactions that induce the degradation of muscle proteins, the synthesis of muscle proteins increase and as a result the number of muscle fiber increases or the size of muscle increases, which is called muscle hypertrophy. Myocyte differentiation and muscle formation are regulated by various muscle regulatory factors such as myoD, myf5, myogenin or mrf4. Among them, myoD initiates the expression of genes specific for muscle differentiation and induces the differentiation of mesenchymal stem cells into myoblasts. Myogenin, which is regulated by myoD, is the most important factor in the binding of myoblasts and is involved in the formation of myotubes. Muscle fibers formed by the process above are bundled to form muscle at last.

On the other hand, when the signaling reactions that induce the degradation of muscle proteins occur more than the signaling reactions that induce the synthesis of muscle proteins, muscle wasting diseases such as muscular atrophy can be developed. Muscle wasting induced by chronic diseases causes the early loss of mobility and increases the risk of disease associated death. Muscle wasting caused by not using muscle is a particularly serious problem in older people, which can increase fracture rate as well as permanent helplessness and premature death. Approximately 24% of aged people at the age between 65 and 70 are experiencing muscular atrophy due to aging, and about 20% of them are experiencing loss of myofunction. As the human body gets aged, the secretion of such hormones involved in anabolism to synthesize protein, for example growth hormones, sex hormones and insulin-like growth factors, is reduced, so that the synthesis of muscle proteins decreases and the level of tumor necrosis factor-alpha (TNF-α), a circulating inflammatory cytokine, increases. TNF-α is fused with damaged muscle fibers or inhibits the differentiation thereof, and accordingly it accelerates catabolism, which is a function to decompose muscle proteins, resulting in the loss of skeletal muscle tissues.

Leucine is one of the three branched-chain amino acids that play the most important role in muscle formation. It is not only a substrate for protein synthesis but also a nutrient to send a signal that regulates protein metabolism. When leucine was orally administered to rats, the rate of skeletal muscle protein increased (Crozier S J et al., J Nutr. 135:376-382, 2005). On the other hand, when leucine was eliminated, the protein synthesis was suppressed (Stipanuk M H, Nutr Rev. 65:122-129, 2007). Leucine mediated protein synthesis is affected by mTORC1 (mammalian target of rapamycin complex 1) composed of mTOR (mammalian target of rapamycin), raptor, GβL and Rheb. mTORC1 regulates cell growth by integrating extracellular and intracellular signals such as mitogen, cell energy status, oxygen level and amino acid availability, etc. When mTORC1 is activated, ribosomal S6 kinase 1 (S6K1) and eukaryotic initiator 4E-binding protein 1 (4EBP1) which regulate protein synthesis at translation initiation are phosphorylated.

mTOR is a serine/threonine protein kinase that regulates cell growth, cell proliferation, cell mobility, cell survival, autophagy, protein synthesis and translation by stimuli such as growth factor, nutrition and stress. The mechanism of mTOR is also related to metabolic diseases including obesity and diabetes, and aging induced diseases such as neurodegenerative disease and cardiovascular disease, as well as lifespan control.

Leucyl-tRNA synthetase (LRS) is a class I enzyme of aminoacyl-tRNA synthetase (ARS), an enzyme that is essential for protein synthesis and survival and activates amino acids to associate with tRNA. In higher eukaryotic cells, LRS exists as a component of ARS complex comprising 9 different tRNA synthetases and 3 non-enzymatic components. LRS recognizes leucine, which plays the most important role in muscle formation, for protein synthesis and muscle formation. LRS and its product, Ap4A, act as signaling regulators in immune response mediated by gene expression. If LRS is not working properly, diseases such as cancer, diabetes and aging can be caused.

Phospholipase D (PLD) catalyzes hydrolysis of phosphatidylcholine (PC) to produce phosphatidic acid (PA) that binds to the FKBP12-rapamycin binding domain of mTOR. PLD1 and PA not only mediate the activation of mTORC1 by mitogen but also mediate the activation of mTORC1 by Vps34 (vacuolar protein sorting 34) induced by amino acids. Vps34 is the only class III P1-3-kinase in mammals, which produces phosphatidylinositol-3-phosphate (PI(3)P) from phosphatidylinositol and activates PLD1 under amino acid stimulation.

Thus, the present inventors tried to develop a muscle enhancer. In the course of developing a muscle enhancer, the present inventors confirmed that LRS (leucyl-tRNA synthetase) interacted directly with Vps34 as an amino acid sensor to activate Vps34, Vps34-PLD1 was necessary for the activation of LRS of mTORC1, and UNE-L domain of LRS was necessary for the activation of Vps34 and PLD1, which were important in the activation of mTORC1, leading to the completion of the present invention.

SUMMARY OF THE INVENTION

Invention to provide a composition comprising the UNE-L domain of leucyl-tRNA synthetase or a polynucleotide encoding the same for increasing muscle.

It is another object of the present invention to provide a composition comprising the UNE-L domain of leucyl-tRNA synthetase or a polynucleotide encoding the same for the treatment of muscle disease.

To achieve the above objects, the present invention provides a composition comprising the UNE-L domain of leucyl-tRNA synthetase or a polynucleotide encoding the same as an effective ingredient for increasing muscle.

The present invention also provides a method for increasing muscle, which comprises a step of administering a pharmaceutically effective dose of the UNE-L domain of leucyl-tRNA synthetase or a polynucleotide encoding the same to a subject.

The present invention also provides a use of a composition comprising the UNE-L domain of leucyl-tRNA synthetase or a polynucleotide encoding the same for increasing muscle.

The present invention also provides a pharmaceutical composition comprising the UNE-L domain of leucyl-tRNA synthetase or a polynucleotide encoding the same as an effective ingredient for the prevention or treatment of muscle disease.

The present invention also provides a method for preventing or treating muscle disease, which comprises a step of administering a pharmaceutically effective dose of the UNE-L domain of leucyl-tRNA synthetase or a polynucleotide encoding the same to a subject.

The present invention also provides a use of a pharmaceutical composition comprising the UNE-L domain of leucyl-tRNA synthetase or a polynucleotide encoding the same for the prevention or treatment of muscle disease.

In addition, the present invention provides a screening method of a candidate substance for the prevention or treatment of muscle disease.

Advantageous Effect

The UNE-L domain of LRS according to the present invention is a site that regulates Vps34, so that the domain activates mTORC1 involved in protein synthesis and increases myocyte differentiation and muscle fiber regeneration, suggesting that the domain can be effectively used for muscle augmentation.

