Laboratory of Molecular Pathology, Department of Health Sciences, Università del Piemonte Orientale "A. Avogadro", 13100 Novara, Italy.
Biomolecules. 2022 Aug 2;12(8):1069. doi: 10.3390/biom12081069.
Alternative splicing allows the synthesis of different protein variants starting from a single gene. Human Beclin 1 () is a key autophagy regulator that acts as haploinsufficient tumor suppressor since its decreased expression correlates with tumorigenesis and poor prognosis in cancer patients. Recent studies show that BECN1 mRNA undergoes alternative splicing. Here, we report on the isolation and molecular and functional characterization of three transcript variants (named BECN1-α, -β and -γ) in human cancer cells. In ovarian cancer NIHOVCAR3, these splicing variants were found along with the canonical . BECN1-α lacks 143 nucleotides at its C-terminus and corresponds to a variant previously described. BECN1-β and -γ lack the BCL2 homology 3 domain and other regions at their C-termini. Following overexpression in breast cancer cells MDA-MB231, we found that BECN1-α stimulates autophagy. Specifically, BECN1-α binds to Parkin and stimulates mitophagy. On the contrary, BECN1-β reduces autophagy with a dominant negative effect over the endogenous isoform. BECN1-γ maintains its ability to interact with the vacuolar protein sorting 34 and only has a slight effect on autophagy. It is possible that cancer cells utilize the alternative splicing of BECN1 for modulating autophagy and mitophagy in response to environmental stresses.
可变剪接允许从单个基因合成不同的蛋白质变体。人类 Beclin 1 () 是一种关键的自噬调节剂，作为单等位基因肿瘤抑制因子发挥作用，因为其表达降低与癌症患者的肿瘤发生和预后不良相关。最近的研究表明，BECN1 mRNA 经历可变剪接。在这里，我们报告了在人类癌细胞中分离和鉴定三种 转录变体（命名为 BECN1-α、-β 和 -γ）的分子和功能特征。在卵巢癌细胞 NIHOVCAR3 中，这些剪接变体与经典的 一起发现。BECN1-α 在其 C 末端缺少 143 个核苷酸，对应于先前描述的变体。BECN1-β 和 -γ 在其 C 末端缺乏 BCL2 同源性 3 结构域和其他区域。在乳腺癌细胞 MDA-MB231 中转染后，我们发现 BECN1-α 刺激自噬。具体来说，BECN1-α 与 Parkin 结合并刺激线粒体自噬。相反，BECN1-β 通过对内源性 同种型的显性负作用降低自噬。BECN1-γ 保持与液泡蛋白分选 34 相互作用的能力，仅对自噬产生轻微影响。癌细胞可能利用 BECN1 的可变剪接来调节自噬和线粒体自噬，以响应环境应激。
