STAT3

1. 본문

Signal Transducer and Activator of Transcription 3 (STAT3) is a protein encoded by the *STAT3* gene in humans and is a member of the STAT protein family. It functions as a transcription factor, playing a crucial role in various cellular processes.

Here's a breakdown of STAT3's key aspects:
Function:

• Transcription Factor: Once activated, STAT3 translocates to the cell nucleus and binds to specific DNA sequences, regulating the expression of various genes.
• Signal Transduction: STAT3 is activated in response to cytokines and growth factors, such as interferons, epidermal growth factor (EGF), interleukin (IL-)5, and IL-6. Receptor-associated Janus kinases (JAKs) phosphorylate STAT3, causing it to form dimers and move to the nucleus.
• Cellular Processes: STAT3 mediates the expression of genes involved in cell growth, division, movement, apoptosis, and differentiation.
• Immune System: STAT3 is involved in immune cell maturation, particularly T and B cells, controlling responses to pathogens like bacteria and fungi. It also regulates inflammation and plays a role in allergic reactions. It is essential for the differentiation of T helper 17 (Th17) cells.
• Skeletal System: It is involved in forming specialized cells responsible for building and breaking down bone tissue.
• Other roles: STAT3 mediates the effects of leptin on the production of melanocortin, energy homeostasis, and lactation. It also plays a part in cell cycle regulation and may induce apoptosis.

• Phosphorylation of tyrosine 705 is a key step in STAT3 activation, occurring in response to various ligands.
• Phosphorylation of serine 727 by mitogen-activated protein kinases (MAPK) and c-src non-receptor tyrosine kinase can also activate STAT3.

• Hyper IgE Syndrome: Loss-of-function mutations in STAT3 can cause Hyper IgE syndrome (also known as Job's Syndrome), an immunodeficiency disorder.
• Cancer: Augmented STAT3 activity has been observed in a large percentage of human tumors (as many as 50%).
• Autoimmune diseases: STAT3 plays a role in the differentiation of TH17 helper T cells, which have been implicated in a variety of autoimmune diseases.
• Viral Infections: Hyperactivation of STAT3 can occur during viral infections, including COVID-19.
• Embryonic Development: STAT3 is essential for early embryonic development, particularly during gastrulation. STAT3 activation is necessary for the self-renewal of embryonic stem cells (ESCs).

• Acetylation can promote STAT3's transcriptional activity and cell differentiation.
• Deacetylation and oxidation of lysine residues can inhibit differentiation.