Shing Jennifer C, Lindquist Lonn D, Borgese Nica, Bram Richard J
Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA.
Consiglio Nazionale delle Ricerche Institute of Neuroscience, Milan, Italy.
Cell Death Discov. 2017 May 29;3:16098. doi: 10.1038/cddiscovery.2016.98. eCollection 2017.
Calcium-modulating cyclophilin ligand (CAML) is an endoplasmic reticulum (ER) protein that functions, along with WRB and TRC40, to mediate tail-anchored (TA) protein insertion into the ER membrane. Physiologic roles for CAML include endocytic trafficking, intracellular calcium signaling, and the survival and proliferation of specialized immune cells, recently attributed to its requirement for TA protein insertion. To identify a possible role for CAML in cancer cells, we generated transgenic mice that carry a tamoxifen-inducible deletion allele of . In multiple B-cell lymphoma cell lines derived from these mice, homozygous loss of activated apoptosis. Cell death was blocked by Bcl-2/Bcl-x overexpression; however, rescue from apoptosis was insufficient to restore proliferation. Tumors established from an lymphoma cell line completely regressed after tamoxifen administration, suggesting that CAML is also required for these cancer cells to survive and grow . Cell cycle analyses of -deleted lymphoma cells revealed an arrest in G2/M, accompanied by low expression of the mitotic marker, phospho-histone H3 (Ser10). Surprisingly, lymphoma cell viability did not depend on the domain of CAML required for its interaction with TRC40. Furthermore, a small protein fragment consisting of the C-terminal 111 amino acid residues of CAML, encompassing the WRB-binding domain, was sufficient to rescue growth and survival of -deleted lymphoma cells. Critically, this minimal region of CAML did not restore TA protein insertion in knockout cells. Taken together, these data reveal an essential role for CAML in supporting survival and mitotic progression in Myc-driven lymphomas that is independent of its TA protein insertion function.
钙调亲环素配体（CAML）是一种内质网（ER）蛋白，它与WRB和TRC40共同发挥作用，介导尾锚定（TA）蛋白插入内质网膜。CAML的生理作用包括内吞运输、细胞内钙信号传导以及特定免疫细胞的存活和增殖，最近这些作用归因于其对TA蛋白插入的需求。为了确定CAML在癌细胞中的可能作用，我们构建了携带他莫昔芬诱导型缺失等位基因的转基因小鼠。在源自这些小鼠的多个B细胞淋巴瘤细胞系中，纯合缺失激活了细胞凋亡。细胞死亡被Bcl-2/Bcl-x过表达所阻断；然而，从凋亡中挽救不足以恢复增殖。用淋巴瘤细胞系建立的肿瘤在给予他莫昔芬后完全消退，这表明CAML也是这些癌细胞存活和生长所必需的。对缺失的淋巴瘤细胞进行细胞周期分析发现细胞停滞在G2/M期，同时有丝分裂标记物磷酸化组蛋白H3（Ser10）的表达较低。令人惊讶的是，淋巴瘤细胞的活力并不依赖于CAML与TRC40相互作用所需的结构域。此外，一个由CAML的C末端111个氨基酸残基组成的小蛋白片段，包含WRB结合结构域，足以挽救缺失的淋巴瘤细胞的生长和存活。至关重要的是，CAML的这个最小区域并不能恢复敲除细胞中TA蛋白的插入。综上所述，这些数据揭示了CAML在支持Myc驱动的淋巴瘤的存活和有丝分裂进程中起着至关重要的作用，这与其TA蛋白插入功能无关。
