J Biol Chem

J Biol Chem. block trafficking c-FMS inhibitor out of the trans Golgi network also inhibits apical but not ciliary delivery. These results suggest that newly synthesized Personal computer1 requires unique pathways to the ciliary and apical membranes. Ciliary Personal computer1 appears to by-pass Brefeldin A sensitive Golgi compartments, while apical delivery of Personal computer1 c-FMS inhibitor traverses these compartments. family of cation channel with six transmembrane domains. It is most abundantly localized to the endoplasmic reticulum 21, 22 and is also indicated in the primary cilium. Personal computer1 and Personal computer2 form a complex that is stabilized by interlocking coiled-coil domains present in each of their intracellular C-termini 23,24, and they are thought to interact in this fashion in the primary cilium. The Personal computer1 and Personal computer2 complex appears to participate in several processes, including calcium signaling, mechano- and chemosensation, and the modulation of signaling cascades such as the JAK/STAT, AP1 and the Wnt pathways 25. The connection between Personal computer1 and Personal computer2 governs aspects of the function and the localization of both proteins 13,16,23,26C29. Cilia contain a unique group of resident membrane and soluble proteins, and the delivery of these proteins into the cilium is definitely thought to be a tightly controlled, multi-step process that begins with the docking of cargo-carrying vesicles to elements of the BBSome protein complex at the base of the cilia 30. Ciliary proteins then travel through a transition zone at the base of the cilium that appears to serve as a selectivity filter that participates in determining which proteins can enter and exit the cilium. Proteins that are permitted to pass through the transition zone consequently traffic along the ciliary axoneme, which serves as the scaffolding on which the molecular motor-driven intraflagellar transport of selected ciliary proteins takes place31. Proteins that are targeted to the apical plasma membrane are generally believed to be delivered through the classical secretory c-FMS inhibitor pathway32C34. In the case of apical proteins, this pathway entails sequential, transient residence in the ER and the Golgi complex, after which they may pass through one or more endosomal compartments, including the common or apical endosomes, or apical early endosome, to the apical plasma membrane 35,36. An interesting subset of cell surface and ciliary proteins, however, appear to utilize a Golgi-bypass pathway that either completely avoids the Golgi complex or that involves unique patterns of residence in or transit through Golgi sub-compartments 32,33,37. Personal computer2, for example, appears to follow a route to the cilium that includes passage through the cis-Golgi compartment but bypasses the medial and trans-Golgi compartments 37C39. Attempts to characterize these non-classical, Golgi-independent protein trafficking pathways often use Brefeldin-A (BFA), a Mouse monoclonal to ZBTB7B fungal metabolite that prevents the assembly of the COPI coating complexes necessary for the anterograde trafficking of proteins between the ER and Golgi complex 40. While BFA treatment blocks anterograde movement of proteins out of the ER, it allows retrograde movement back into the ER, efficiently leading to a merger of the cis- and medial Golgi compartments with the ER 41. BFA treatment also induces the merger of the trans-Golgi compartment with the recycling endosomal system but does not impair the cycling of proteins between the plasma membrane and the endosomes 42. In addition, protein trafficking though the Golgi complex in mammalian cells can also be clogged by incubating cells at 20C 43C45. The mechanism through which this 20C treatment reversibly blocks Golgi trafficking through the trans-Golgi network remains unelucidated. Experiments in which polarized epithelial cells were treated with BFA show that a growing list of plasma membrane parts, including membrane lipids as well as adhesion and signaling proteins, can be trafficked to the cell surface via non-canonical, BFA-insensitive routes 46. Some of these proteins traverse the Intermediate Compartment (IC), a collection of tubules that are defined by the presence of Rab1 and by resistance to BFA-induced COPI uncoating 34. The cystic fibrosis transmembrane conductance regulator chloride channel is an example of a protein that appears to bypass at least a portion of the Golgi complex and that manifests transient IC residence, moving through a pericentrosomal subcompartment of the IC on its non-canonical path to the c-FMS inhibitor plasma membrane 47. The work offered here examines the delivery of Personal computer1 to the apical and ciliary membranes. We have developed a technique that uses immunofluorescence labeling to visualize a temporally defined cohort.