CLPTM1L modulates membrane lipid rafts to promote tumor EGFR signaling.

The plasma membrane dynamically organizes into specialized lipid domains to sustain cell proliferative signaling, yet the regu-latory mechanisms driving this process, especially during tumor progression, remain poorly understood. Here, we uncover cleft lip and palate transmembrane protein 1-like protein (CLPTM1L), an endoplasmic reticulum-localized lipid scramblase, as a critical regulator of membrane raft formation and the epidermal growth factor receptor (EGFR)-mediated proliferative signaling in cancer. High CLPTM1L expression was significantly associated with poor patient survival in glioblastoma (GBM), the most aggressive brain cancer. Depletion of CLPTM1L disrupts cellular lipid homeostasis and results in a substantial loss of membrane raft components, including glycosphingolipids and glycosylphosphatidylinositol (GPI)-anchored proteins. The cell-surface level of EGFR, which colocalizes with raft marker GM1, is markedly reduced upon CLPTM1L loss. We show that CLPTM1L-mediated raft remodeling promotes EGFR signaling and drives cell proliferation in both cancer and non-cancer cells. In GBM mouse models, CLPTM1L depletion inhibits EGFR signaling and profoundly impairs orthotopic tumor growth. Our work establishes CLPTM1L as a key regulator of membrane raft domain formation and highlights its critical role in cancer proliferative signaling.