Cytosolic phospholipase A₂ε drives recycling through the clathrin-independent endocytic route.

Previous studies have demonstrated that membrane tubule-mediated transport events in biosynthetic and endocytic routes require phospholipase A2 (PLA2) activity. Here, we show that cytosolic phospholipase A2ε (cPLA2ε, also known as PLA2G4E) is targeted to the membrane compartments of the clathrin-independent endocytic route through a C-terminal stretch of positively charged amino acids, which allows the enzyme to interact with phosphoinositide lipids [especially PI(4,5)P2] that are enriched in clathrin-independent endosomes. Ablation of cPLA2ε suppressed the formation of tubular elements that carry internalized clathrin-independent cargoes, such as MHC-I, CD147 and CD55, back to the cell surface and, therefore, caused their intracellular retention.

Group IV phospholipase A(2)alpha controls the formation of inter-cisternal continuities involved in intra-Golgi transport.

The organization of intra-Golgi trafficking and the nature of the transport intermediates involved (e.g., vesicles, tubules, or tubular continuities) remain incompletely understood.

Faciogenital dysplasia protein (FGD1) regulates export of cargo proteins from the golgi complex via Cdc42 activation.

Mutations in the FGD1 gene are responsible for the X-linked disorder known as faciogenital dysplasia (FGDY). FGD1 encodes a guanine nucleotide exchange factor that specifically activates the GTPase Cdc42. In turn, Cdc42 is an important regulator of membrane trafficking, although little is known about FGD1 involvement in this process.

Ypt32p and Mlc1p bind within the vesicle binding region of the class V myosin Myo2p globular tail domain.

Myosin V is an actin-based motor essential for a variety of cellular processes including skin pigmentation, cell separation and synaptic transmission. Myosin V transports organelles, vesicles and mRNA by binding, directly or indirectly, to cargo-bound receptors via its C-terminal globular tail domain (GTD). We have used the budding yeast myosin V Myo2p to shed light on the mechanism of how Myo2p interacts with post-Golgi carriers.

Defective intracellular trafficking of uromodulin mutant isoforms.

Medullary cystic kidney disease/familial juvenile hyperuricemic nephropathy (MCKD/FJHN) are autosomal dominant renal disorders characterized by tubulo-interstitial fibrosis, hyperuricemia and medullary cysts. They are caused by mutations in the gene encoding uromodulin, the most abundant protein in urine. Uromodulin (or Tamm-Horsfall protein) is a glycoprotein that is exclusively expressed by epithelial tubular cells of the thick ascending limb of Henle's loop and distal convoluted tubule.

Ultrastructure of long-range transport carriers moving from the trans Golgi network to peripheral endosomes.

The delivery of mannose 6-phosphate receptors carrying lysosomal hydrolases from the trans-Golgi network (TGN) to the endosomal system is mediated by selective incorporation of the receptor-hydrolase complexes into vesicular transport carriers (TCs) that are coated with clathrin and the adaptor proteins, GGA and AP-1. Previous electron microscopy (EM) and biochemical studies have shown that these TCs consist of spherical coated vesicles with a diameter of 60-100 nm. The use of fluorescent live cell imaging, however, has revealed that at least some of this transport relies on a subset of apparently larger and highly pleiomorphic carriers that detach from the TGN and translocate toward the peripheral cytoplasm until they meet with distally located endosomes.

Secretory traffic triggers the formation of tubular continuities across Golgi sub-compartments.

The organization of secretory traffic remains unclear, mainly because of the complex structure and dynamics of the secretory pathway. We have thus studied a simplified system, a single synchronized traffic wave crossing an individual Golgi stack, using electron tomography. Endoplasmic-reticulum-to-Golgi carriers join the stack by fusing with cis cisternae and induce the formation of intercisternal tubules, through which they redistribute their contents throughout the stack.

Golgi enzymes are enriched in perforated zones of golgi cisternae but are depleted in COPI vesicles.

In the most widely accepted version of the cisternal maturation/progression model of intra-Golgi transport, the polarity of the Golgi complex is maintained by retrograde transport of Golgi enzymes in COPI-coated vesicles. By analyzing enzyme localization in relation to the three-dimensional ultrastructure of the Golgi complex, we now observe that Golgi enzymes are depleted in COPI-coated buds and 50- to 60-nm COPI-dependent vesicles in a variety of different cell types. Instead, we find that Golgi enzymes are concentrated in the perforated zones of cisternal rims both in vivo and in a cell-free system.

Delivery of raft-associated, GPI-anchored proteins to the apical surface of polarized MDCK cells by a transcytotic pathway.

Epithelial cell polarity depends on mechanisms for targeting proteins to different plasma membrane domains. Here, we dissect the pathway for apical delivery of several raft-associated, glycosyl phosphatidylinositol (GPI)-anchored proteins in polarized MDCK cells using live-cell imaging and selective inhibition of apical or basolateral exocytosis. Rather than trafficking directly from the trans-Golgi network (TGN) to the apical plasma membrane as previously thought, the GPI-anchored proteins followed an indirect, transcytotic route.

Mechanism of constitutive export from the golgi: bulk flow via the formation, protrusion, and en bloc cleavage of large trans-golgi network tubular domains.

Transport of constitutive cargo proteins from the Golgi complex to the plasma membrane (PM) is known to be mediated by large tubular-saccular carriers moving along microtubules. However, the process by which these large structures emerge from the trans-Golgi network (TGN) remains unclear. Here, we address the question of the formation of Golgi-to-PM carriers (GPCs) by using a suitable cluster of morphological techniques, providing an integrated view of their dynamics and three-dimensional structure.