The LysRS-Ap4A-MITF Signaling Pathway
The LysRS-Ap4A-MITF signaling pathway was first discovered in mast cells, in which, the MAPK pathway is activated upon allergen stimulation. Lysyl-tRNA synthetase (LysRS), which normally resides in the multisynthetase complex with other tRNA sythetases, is phosphorylated on Serine 207 in a MAPK-dependent manner. This phosphorylation causes LysRS to change its conformation, detach from the complex and translocate into the nucleus, where it associates with the MITF-HINT1 inhibitory complex. The conformational change switches LysRS activity from aminoacylation of Lysine tRNA to diadenosine tetraphosphate (Ap4A) production. Ap4A binds to HINT1, which releases MITF from the inhibitory complex, allowing it to transcribe its target genes. Activation of the LysRS-Ap4A-MITF signaling pathway by isoproterenol has been confirmed in cardiomyocytes, where MITF is a major regulator of cardiac growth and hypertrophy.
Read more about this topic: Microphthalmia-associated Transcription Factor
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