Activin B  (激活素 B)

Activin B 是一种 TGFβ 超家族细胞因子，是激活素 βB 亚基的同源二聚体。Activin B 与 II 型跨膜丝氨酸-苏氨酸激酶受体 (ACTRIIA 或 ACTRIIB) 结合，进而激活 I 型受体 (ACTRI)，从而磷酸化并激活经典的 SMAD 信号通路。激活素是 TGF-β 超家族的成员，首先从猪卵巢卵泡液中分离出来，并被确定为促卵泡激素释放的激活因子。Activin B 存在于大多数组织中，包括胎盘、生殖器官、骨髓和大脑。Activin B 是炎症和免疫的调节剂，还参与癌症或伤口愈合过程^[1][2][3]< sup>[4].
激活素存在不同的附加作用，包括对细胞生长和分化、胚胎发生调节、生殖系统发育、伤口愈合、干细胞分化和免疫反应调节的广泛而复杂的作用。激活素通过丝氨酸/苏氨酸蛋白激酶 (MAPKs) 信号通路发挥其生物学功能。Activin B 也可能通过 IC 型激活素受体 (ACVR1C (ALK7)) 发出信号。 I 型受体通过 SMAD2/3 激活磷酸化级联来启动信号级联，该磷酸化级联与 SMAD4 复合并转运至细胞核以调节基因转录^[1][2][3]。

Activin B, a TGFβ superfamily cytokine, is a homodimer of activin βB subunits. Activin B binds to type II transmembrane serine-threonine kinase receptors (ACTRIIA or ACTRIIB) which, in turn, activate type I receptors (ACTRI) that phosphorylate and activate canonical SMAD signaling pathways. Activins, members of the TGF-β superfamily, are first isolated from porcine ovarian follicular fluid and identified as activating factors for the release of follicle stimulating hormone. Activin B found in most tissues including placenta, reproductive organs, bone marrow, and brain. Activin B is a regulator of inflammation and immunity, and also involved in cancer or wound healing processes^[1][2][3][4].
Activins exist different additional roles, including broad and complex effects on cell growth and differentiation, regulation of embryogenesis, development of the reproductive system, wound healing, stem cell differentiation and regulation of immune response. Activins exert their biological functions through the serine/threonine protein kinase (MAPKs) signaling pathways. Activin B might also signal through the type IC activin receptors (ACVR1C (ALK7)). The type I receptor initiates a signaling cascade by activating a phosphorylation cascade through SMAD2/3 that complexes with SMAD4 and translocates to the cell nucleus to modulate gene transcription^[1][2][3].

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