LAMP1/CD107a is required for efficient perforin delivery to lytic granules and NK-cell cytotoxicity

Abstract

Key Points• LAMP1 silencing inhibits cytotoxicity of human NK cells.• LAMP1 is important for perforin trafficking to the lytic granules and granule movement.Secretory lysosomes of natural killer (NK) cells, containing perforin and granzymes, are indispensable for NK-cell cytotoxicity because their release results in the induction of target-cell apoptosis. Lysosome-associated membrane protein (LAMP) 1/CD107a is used as a marker for NK-cell degranulation, but its role in NK-cell biology is unknown. We show that LAMP1 silencing causes inhibition of NK-cell cytotoxicity, as LAMP1 RNA interference (RNAi) cells fail to deliver granzyme B to target cells. Reduction of LAMP1 expression affects the movement of lytic granules and results in decreased levels of perforin, but not granzyme B, in the granules. In LAMP1 RNAi cells, more perforin is retained outside of lysosomal compartments in trans-Golgi network-derived transport vesicles. Disruption of expression of LAMP1 binding partner, adaptor protein 1 (AP-1) sorting complex, also causes retention of perforin in the transport vesicles and inhibits cytotoxicity, indicating that the interaction between AP-1 sorting complex and LAMP1 on the surface of the transport vesicles is important for perforin trafficking to lytic granules. We conclude that the decreased level of perforin in lytic granules of LAMP1-deficient cells, combined with disturbed motility of the lytic granules, leads to the inability to deliver apoptosis-inducing granzyme B to target cells and to inhibition of NK-cell cytotoxicity. (Blood. 2013;121(23):4672-4683)

Gap Junction Intercellular Communications Regulate NK Cell Activation and Modulate NK Cytotoxic Capacity

“…During NK cell-mediated cytotoxicity, a transient Ca 2+ influx is induced in the target cells, which is necessary for the apoptosis triggered by the endocytosed GrB (21,37,38). It is known that Cx43 regulates Ca 2+ influx in various cell types (39), and we have previously reported that Cx43 regulates Ca 2+ signaling at the IS in T cells (14).…”

“…5B). CD107a (LAMP-1)-deficient cells have reduced levels of perforin in lytic granules and disturbed motility of the lytic granules, which leads to the inability to deliver apoptosis-inducing GrB to target cells and to the inhibition of NK cell cytotoxicity (36,37). We evaluated CD107a expression on the surface of NK cells; however, no difference in CD107a levels were observed upon blockade of Cx43-GJs in NK cells and K562 cells (Fig.…”

Mechanisms and functions of lysosome positioning

“…For example, the lysosomal Ca 2+ -sensor ALG-2 (also known as PDCD6) promotes interaction of the lysosomal Ca 2+ channel transient receptor potential mucolipin 1 (TRPMNL1 or MCOLN1) with dynein-dynactin to regulate centripetal transport of lysosomes in response to changes in Ca 2+ levels (Li et al, 2016b). There are also lysosomal transmembrane proteins that regulate retrograde transport, such as LAMP-1 and LAMP-2, which promote coupling of lysosomes to dyneindynactin (Huynh et al, 2007;Krzewski et al, 2013), and transmembrane protein 106B (TMEM106B), which inhibits retrograde transport of lysosomes in neuronal dendrites through interaction with the microtubule-associated protein 6 (MAP6) (Schwenk et al, 2014). Finally, the snapin subunit of the BORC and BLOC-1 complexes (Pu et al, 2015) has also been reported to couple lysosomes to dynein, particularly in hippocampal neurons (Cai et al, 2010).…”

High-dose cyclophosphamide induces specific tumor immunity with concomitant recruitment of LAMP1/CD107a-expressing CD4-positive T cells into tumor sites

“…LAMP1/CD107a appears on the cell surface following the fusion of lysosomes with the plasma membrane, and therefore is therefore used as a functional marker of degranulation of CD8 + CTLs [24] and NK cells [25]. Moreover, LAMP1/CD107a is required for efficient perforin delivery to lytic granules and subsequent cytotoxicity [17]. We observed that infiltrated CD4 + T cells consistently expressed constantly higher levels of LAMP1/CD107a and additional inflammatory cytokines, particularly type I interferon [10,26,27].…”