Recruitment of arfaptins to the trans-Golgi network by PI(4)P and their involvement in cargo export

Abstract

The BAR (Bin/Amphiphysin/Rvs) domain proteins arfaptin1 and arfaptin2 are localized to the trans-Golgi network (TGN) and, by virtue of their ability to sense and/or generate membrane curvature, could play an important role in the biogenesis of transport carriers. We report that arfaptins contain an amphipathic helix (AH) preceding the BAR domain, which is essential for their binding to phosphatidylinositol 4-phosphate (PI(4)P)-containing liposomes and the TGN of mammalian cells. The binding of arfaptin1, but not arfaptin2, to PI(4)P is regulated by protein kinase D (PKD) mediated phosphorylation at Ser100 within the AH. We also found that only arfaptin1 is required for the PKD-dependent trafficking of chromogranin A by the regulated secretory pathway. Altogether, these findings reveal the importance of PI(4)P and PKD in the recruitment of arfaptins at the TGN and their requirement in the events leading to the biogenesis of secretory storage granules.

A Complex Comprising Phosphatidylinositol 4-Kinase IIIβ, ACBD3, and Aichi Virus Proteins Enhances Phosphatidylinositol 4-Phosphate Synthesis and Is Critical for Formation of the Viral Replication Complex

“…Further, it is likely that PI4P is required to anchor PI4P-binding proteins that induce membrane rearrangement. Proteins that bind to PI4P within the Golgi apparatus include oxysterol-binding protein-1 (OSBP1), ceramide transfer protein (CERT) or four phosphate adaptor protein 1 (FAPP1), FAPP2, Golgi phosphoprotein 3 (GOLPH3) (13), and Arfaptin1 and Arfaptin2 (40). FAPP1 and FAPP2 regulate lipid transport (41,42) and Golgi-to-plasma membrane transport (43,44) and induce membrane tubulation (45,46).…”

Multiple activities of Arl1 GTPase in the trans-Golgi network

“…Genetic alterations of Arl1 as well as its effectors were used to characterize developmental and physiological phenotypes (summarized in Fig. 1) (Chang et al, 2015;Cruz-Garcia et al, 2013;Eiseler et al, 2016;Gehart et al, 2012;Hesse et al, 2013;Hsu et al, 2016;Labbaoui et al, 2017;Lieu et al, 2008;Liu et al, 2006;Lock et al, 2005;Marešová and Sychrová, 2010;Marešová et al, 2012;Murray and Stow, 2014;Price et al, 2005;Torres et al, 2014;Yang and Rosenwald, 2016). In mammalian cells, these functions affect a wide range of fundamental cellular processes, including cell polarity (Lock et al, 2005), innate immunity (Bremond et al, 2009;Lieu et al, 2008;Murray and Stow, 2014;Stanley et al, 2012), lipid droplet and chylomicron formation (Hesse et al, 2013;Jaschke et al, 2012), as well as the secretion of insulin (Gehart et al, 2012), chromogranin A (CruzGarcia et al, 2013) and matrix metalloproteinases (MMPs) (Eiseler et al, 2016).…”

“…Human Arl1 also has a role in protein secretion mediated by arfaptins, which were shown to play a role in maintaining insulin secretion from pancreatic β cells (Gehart et al, 2012) and are required for trafficking of the acidic secretory glycoprotein chromogranin A (Cruz-Garcia et al, 2013) from the TGN in neuroendocrine cells. Interestingly, a multi-protein complex comprising Arl1, PKD2, Arf1 and arfaptin-2 was found to regulate the constitutive secretion of endogenous MMP7 and MMP2 cargos in pancreatic cells (Eiseler et al, 2016).…”

“…Glucose-stimulated insulin secretion might, thus, be regulated by modulating arfaptin-1b phosphorylation and by controlling Arfmediated insulin granule fission at the Golgi (Gehart et al, 2012). In contrast, arfaptin-1a − the short isoform of arfaptin-1 − is phosphorylated by PKD2 and required for the regulatory secretion of chromogranin A in neuroendocrine cells, a process in which arfaptin-2 does not have a major role (Cruz-Garcia et al, 2013). Interestingly, PKD2, but not PKD1, assembles in a multi-protein complex consisting of Arl1, PKD2, Arf1 and arfaptin-2 at the TGN.…”

Analyses of PDE-regulated phosphoproteomes reveal unique and specific cAMP-signaling modules in T cells

“…Of these 55 phosphosites 13 were at canonical PKA consensus sequences and therefore are likely to be directly phosphorylated by PKA. These include ARFIP1 S132 (38,39), ARHGEF2 S886 (40), BAD S152 (41,42), BRAF S446 (43), CAD S1406 (44), CAMKK1 S458 (45), KIF3A S687 (46,47), LASP1 S146(48-50), PTPN7 S44 (51, 52), RCC1 S11(53-55), RPS6 S235 (56), STMN1 S63 (57-59), and TAL1 172 (60,61). In fact, eight of these sitesin ARHGEF2, BAD, CAD, CAMKK1, LASP1, PTPN7, STMN1, and TAL1-have been reported to be substrates of PKA in other cell types.…”