<p>STIM1, a type I transmembrane protein characterized by its extracellular N-terminal domain (STIM1_PM), was initially identified as a plasma membrane (PM)-localized protein with tumor growth suppressor activity. Subsequent studies have identified a role for STIM1_PM in the regulation of store-independent Ca²⁺ entry pathways including arachidonic acid-regulated Ca²⁺ (ARC) channels and constitutive Ca²⁺ entry (CCE). Mechanistically, N-glycosylation facilitates STIM1_PM trafficking and stability at the PM. In this study, we demonstrate that STIM1_PM uniquely exhibits dual topology at the PM, presenting both the expected type I orientation and an alternative type II orientation. Notably, we found that both orientations of STIM1_PM contribute to CCE regulation. Our results confirm that N-glycosylation promotes the N-terminal-out orientation of STIM1_PM, however, here we found it also modulates it’s the receptor’s dual topology. Our findings reveal that STIM1_PM displays dual topology and regulate CCE.</p>