Regulation of Integrin Endocytic Recycling and Chemotactic Cell Migration by Syntaxin 6 and VAMP3 Interaction

Abstract

SummaryIntegrins are the primary receptors of cells adhering to the extracellular matrix, and play key roles in various cellular processes including migration, proliferation and survival. The expression and distribution of integrins at the cell surface is controlled by endocytosis and recycling. The present study examines the function of syntaxin 6 (STX6), a t-SNARE located in the trans-Golgi network, in integrin trafficking. STX6 is overexpressed in many types of human cancer. We show that depletion of STX6 inhibits chemotactic cell migration and the delivery of the laminin receptor a3b1 integrin to the cell surface, whereas STX6 overexpression stimulates chemotactic cell migration, integrin delivery, and integrin-initiated activation of focal adhesion kinase. These data indicate that STX6 plays a ratelimiting role in cell migration and integrin trafficking. In STX6-depleted cells, a3b1 integrin is accumulated in recycling endosomes that contain the v-SNARE VAMP3. Importantly, we show that STX6 and VAMP3 form a v-/t-SNARE complex, VAMP3 is required in a3b1 integrin delivery to the cell surface, and endocytosed a3b1 integrin traffics to both VAMP3 and STX6 compartments. Collectively, our data suggest a new integrin trafficking pathway in which endocytosed integrins are transported from VAMP3-containing recycling endosomes to STX6-containing trans-Golgi network before being recycled to the plasma membrane.

Genome-Wide Small Interfering RNA Screens Reveal VAMP3 as a Novel Host Factor Required for Uukuniemi Virus Late Penetration

“…Rather than mediating endosome-plasma membrane fusion, VAMP3 is actually thought to be involved in autophagosomeendosome fusion (40,41,52,53). It is present on autophagosomes.…”

Role of cholesterol in SNARE-mediated trafficking on intracellular membranes

“…In this context, the ability of SNAREs to bind cholesterol in specific cellular sites could contribute to the establishment of functional links between cholesterol and integrin localization and function. These cholesterol-binding SNAREs include VAMP2, VAMP3 (also known as cellubrevin), STX3, STX4 and SNAP23, which all participate in the recycling of b1 integrin, and VAMP3 and STX6, which determine the levels of cell-surface-associated a5b1 integrin and of FAK (Hulce et al, 2013;Riggs et al, 2012;Tiwari et al, 2011) (see also Fig. 2A and Table 1).…”

“…It has yet to be demonstrated whether these observations are based on some SNAREs functioning as cholesterol sensors in cancer. Indeed, STX6 overexpression increases cell migration, and its expression is elevated in breast, liver and prostate cancers (Riggs et al, 2012), which all have established links to cholesterol homeostasis.…”

On the move: endocytic trafficking in cell migration

“…Loss of SNAP29 caused a longer retention of b1 integrin in intracellular compartments and impaired wound healing [82]. Furthermore, the SNAREs VAMP3 and syntaxin6 were revealed as crucial factors for the surface delivery of integrins in HeLa cells [83]. Loss of syntaxin6, which is located at the trans-Golgi network, or VAMP3, which is present on recycling endosomes, led to the accumulation of a3b1 in perinuclear recycling endosomes and thereby impaired chemotactic cell migration.…”

“…Loss of syntaxin6, which is located at the trans-Golgi network, or VAMP3, which is present on recycling endosomes, led to the accumulation of a3b1 in perinuclear recycling endosomes and thereby impaired chemotactic cell migration. Syntaxin6 und VAMP3 presumably form a SNARE complex that catalyzes vesicle fusion which is necessary for the transport of integrins from VAMP3 positive recycling endosomes to the syntaxin6-containing trans-Golgi network, before they are delivered to the plasma membrane, thus delineating a new transport route [83].…”