OCRL1与ORP4L竞争利用细胞膜PIP2维持细胞Ca2+稳态与生存的作用和机制研究

Ca2+ homeostasis is crucial for cell survival. It has been proved that ORP4L is highly expressed in T-ALL cells and maintains cell Ca2+ signal, its overexpression induced Ca2+ oscillation out-of-balance and cell death. The collaborative mechanism of preventing overreacted Ca2+ signal is poorly understood. In our preliminary study, we found that inositol polyphosphate 5-phosphatase OCRL1 interacts with ORP4L and reduces PIP2 content of plasma membrane; OCRL1 is essential for T-ALL cell survival and its knockdown induced cell death; OCRL1 suppressed the role of ORP4L in Ca2+ release enhancement. We hypothesize that: OCRL1 acts as a functional negative regulator of ORP4L, it prevents excessive PIP2 hydrolysis by PLCβ3, resulting out-of-balance Ca2+ oscillation and cytotoxicity by using plasma membrane PIP2 competitively with ORP4L. In this project, we intent to employ clinical samples, cell lines and mouse model to elucidate this hypothesis, providing new insight into the regulatory mechanism of Ca2+ homeostasis and survival in T-ALL cell.

Ca2+信号稳态对细胞生存至关重要。ORP4L维持T-ALL细胞正常的Ca2+ 信号，但其过表达会导致Ca2+信号节律失衡和细胞死亡，是否存在一个协同机制以防止Ca2+信号过强，值得认真探索。我们前期研究发现：1）PIP2磷酸酶OCRL1在T-ALL细胞中高表达并维持T-ALL细胞生存； 2）OCRL1物理结合ORP4L并降低细胞膜PIP2含量；3）OCRL1抑制ORP4L对Ca2+信号的增强作用。据此我们提出假说：OCRL1是ORP4L的负调控因子，与ORP4L竞争PIP2，限制过量PIP2通过PLCβ3水解产生过强的Ca2+信号和细胞毒性。本课题拟在临床标本、细胞系和小鼠模型中阐明上述假说，以期从细胞膜PIP2利用角度揭示T-ALL 细胞Ca2+信号稳态与生存的系统性调节机制，为T-ALL治疗提供新的思路。