Panoply™ Human LAMP1 Knockdown Stable Cell Line

Lassa virus (LASV) is an arenavirus that enters host cells via a process mediated by its glycoprotein complex (GPC). Following receptor-mediated endocytosis, the virus traffics through the endocytic pathway and is thought to fuse with the late endosomal membrane-a process triggered by low pH and mediated by GPC. A unique feature of LASV entry is the pH-dependent switch from a primary cell-surface receptor (α-dystroglycan) to an endosomal receptor: lysosomal-associated membrane protein (Lamp1). Using wild-type (WT) and Lamp1-knockout (KO) cells, researchers demonstrated that while Lamp1 enhances the efficiency of LASV entry and infection, it is not strictly essential. Subsequent cell-cell and pseudovirus-cell fusion assays revealed that LASV GPC-mediated fusion occurs at a significantly higher pH in the presence of Lamp1 compared to its absence. Consistent with this, LASV enters wild-type (Lamp1-positive) cells via less acidic endosomes, whereas this does not occur in Lamp1-knockout cells. The researchers propose that by raising the pH threshold for fusion, Lamp1 enables LASV particles to exit the endocytic pathway before encountering the more acidic and proteolytically active environments that would otherwise cause extensive viral inactivation. In this manner, Lamp1 boosts the overall efficiency of LASV entry and infection.

Recent reports have identified Lamp1 as an intracellular receptor for LASV. To investigate the function of Lamp1, researchers generated a stable Lamp1 knockdown cell line. This knockdown reduced Lamp1 expression to approximately 15% of the level found in wild-type (WT) cells (Figure 1A). However, across all tested viral inocula, there was no difference in susceptibility between Lamp1 knockdown cells and WT cells to MLV pseudoviruses bearing LASV GPC (and encoding luciferase) (Figure 1A). As LCMV GPC does not interact with Lamp1, LCMV infection was-as expected-unaffected by the reduction in Lamp1 expression (Figure 1B). These results (Figure 1A) indicate that the residual Lamp1 expression in Lamp1 knockdown cells is sufficient to fully support efficient LASV GPC-mediated infection.

Figure 1. Knockdown of Lamp1 does not suppress LASV pseudovirus infection. (Hulseberg C E, et al., 2018)