Integrin endosomal signalling suppresses anoikis

Abstract

Integrin containing focal adhesions (FAs) transmit extracellular signals across the plasma membrane to modulate cell adhesion, signalling and survival. Although integrins are known to undergo continuous endo/exocytic traffic, potential impact of endocytic traffic on integrin-induced signals is unknown. Here, we demonstrate that integrin signalling is not restricted to cell-ECM adhesions and identify an endosomal signalling platform that supports integrin signalling away from the plasma membrane. We show that active focal adhesion kinase (FAK), an established marker of integrin-ECM downstream signalling, localises with active integrins on endosomes. Integrin endocytosis positively regulates adhesion-induced FAK activation, which is early endosome antigen-1 (EEA1) and small GTPase Rab21 dependent. FAK binds directly to purified endosomes and becomes activated on them, suggesting a role for endocytosis in enhancing distinct integrin downstream signalling events. Finally, endosomal integrin signalling contributes to cancer-related processes such as anoikis resistance, anchorage-independence and metastasis.Integrins are heterodimeric cell surface adhesion receptors functioning as integrators of the extracellular matrix (ECM) driven cues, the cellular cytoskeleton and the cellular signalling apparatus 1.Upon adhesion, integrins trigger the formation of plasma-membrane proximal large mechanosensing and signal-transmitting protein clusters depicted as "adhesomes" 2, 3. In addition, integrins undergo constant endocytic traffic to facilitate focal adhesion turnover, cell migration, invasion and cytokinesis 4. For other receptor systems it is well established that endocytic membrane traffic regulates bioavailability of cell-surface molecules and therefore the intensity and/or specificity of receptor-initiated signals 5, 6. Although active integrins and their Correspondence should be addressed to J.I. (johanna.ivaska@utu.fi). Author InformationThe mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the dataset identifier PXD001870 and 10.6019/PXD001870. Authors declare no conflict of interests. Europe PMC Funders GroupAuthor Manuscript Nat Cell Biol. Author manuscript; available in PMC 2016 June 02. Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts ligands have been detected in endosomes 7-9 and increased integrin recycling to the plasma membrane contributes to enhanced signalling of co-trafficked receptor tyrosine kinases10, 11 it has remained unclear whether endocytosed active integrins signal in endosomes. Here, we demonstrate that integrin signalling is not restricted to focal adhesions as previously described and that endocytosis is necessary for full ECM-induced, integrin mediated ERK, AKT and FAK signalling. We find that FAK binds directly to and can become activated on purified endosomes. Moreover, the FERM-domain of FAK is able to bind purified integrin containing endosomes, suggesting the potential for integ...

Low-intensity pulsed ultrasound promotes cell motility through vinculin-controlled Rac1 GTPase activity

“…7A,B) has put forward a model whereby the LIPUS-induced forces lead to internalization of the whole integrin-associated complex that proceeds to maintain a signalling function on the endosome, as has been suggested previously (Alanko et al, 2015;Palamidessi et al, 2008). This model is supported by our findings that many Rab5-positive endosomes contained activated Rac1 (Fig.…”

“…6A). It is likely that FAK signalling to activate Rac1 occurs initially at FAs, rather than at integrin-containing endosomes, which have been reported to contain pFAK-Y397 (Alanko et al, 2015). However, pFAK-Y397 at this compartment could act to sustain Rac1 signalling once LIPUS stimulation has ended.…”

Arf GAPs and molecular motors

“…This activity would be consistent with a coordinated role for AGAP1 in mediating endosome dependent FAK activation, FA assembly and signaling. 90 In this scenario, AGAP1 would be part of the machinery antagonizing microtubule-dependent FAK inactivation and FA dissolution (Fig. 5).…”

The Ser/Thr Kinase MAP4K4 Controls Pro-Metastatic Cell Functions

“…However, compelling evidence indicates that MAP4K4 decreases surface availability of active integrins [17], for example by inactivating integrins via moesin phosphorylation, which concomitantly competes with talin for integrin binding [18], or by accelerating their endosomal trafficking [19].…”

“…microRNA regulation of MAP4K4 expression in cancer microRNAs (miRNAs) are endogenous, small noncoding RNAs, with a length of approximately [19][20][21][22][23][24] nucleotides that negatively regulate gene expression by base pairing complementary sites on the 3'-untranslated region (3'-UTR) of target messenger RNAs [57]. Several MAP4K4-targeting miRNAs were found repressed in tumors, leading thus to increased levels of MAP4K4 expression.…”