The cilium, plural cilia is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projection that extends from the surface of the much larger cell body. Eukaryotic flagella found on sperm cells and many protozoans have a similar structure to motile cilia that enables swimming through liquids; they are longer than cilia and have a different undulating motion.
Intraflagellar transport (IFT) is a bidirectional motility along axoneme microtubules that is essential for the formation (ciliogenesis) and maintenance of most eukaryotic cilia and flagella. It is thought to be required to build all cilia that assemble within a membrane projection from the cell surface. Plasmodium falciparum cilia and the sperm flagella of Drosophila are examples of cilia that assemble in the cytoplasm and do not require IFT. The process of IFT involves movement of large protein complexes called IFT particles or trains from the cell body to the ciliary tip and followed by their return to the cell body. The outward or anterograde movement is powered by kinesin-2 while the inward or retrograde movement is powered by cytoplasmic dynein 2/1b. The IFT particles are composed of about 20 proteins organized in two subcomplexes called complex A and B.
ADP-ribosylation factor 1 is a protein that in humans is encoded by the ARF1 gene.
Kinesin-like protein KIF3A is a protein that in humans is encoded by the KIF3A gene.
Trafficking protein particle complex subunit 3 is a protein that in humans is encoded by the TRAPPC3 gene.
Protein SEC13 homolog is a protein that in humans is encoded by the SEC13 gene.
Kinesin-like protein KIF3B is a protein that in humans is encoded by the KIF3B gene. KIF3B is an N-type protein that complexes with two other kinesin proteins to form two-headed anterograde motors. First, KIF3B forms a heterodimer with KIF3A ; (KIF3A/3B), that is membrane-bound and has ATPase activity. Then KIFAP3 binds to the tail domain to form a heterotrimeric motor. This motor has a plus end-directed microtubule sliding activity that exhibits a velocity of ∼0.3 μm/s a. There are 14 kinesin protein families in the kinesin superfamily and KIF3B is part of the Kinesin-2 family, of kinesins that can all form heterotrimeric complexes. Expression of the three motor subunits is ubiquitous. The KIG3A/3B/KAP3 motors can transport 90 to 160 nm in diameter organelles.
BET1-like protein is a protein that in humans is encoded by the BET1L gene.
Conserved oligomeric Golgi complex subunit 7 is a protein that in humans is encoded by the COG7 gene.
Centriolin is a protein that in humans is encoded by the CNTRL gene. It was previously known as CEP110.
Intraflagellar transport protein 88 homolog is a protein that is encoded by the IFT88 gene.
Conserved oligomeric Golgi complex subunit 4 is a protein that in humans is encoded by the COG4 gene.
Intraflagellar transport protein 57 homolog is a protein that in humans is encoded by the IFT57 gene.
Kinesin-like protein KIF17 is a protein that in humans is encoded by the KIF17 gene. KIF17 and its close relative, C. elegans OSM-3, are members of the kinesin-2 family of plus-end directed microtubule-based motor proteins. In contrast to heterotrimeric kinesin-2 motors, however, KIF17 and OSM-3 form distinct homodimeric complexes. Homodimeric kinesin-2 has been implicated in the transport of NMDA receptors along dendrites for delivery to the dendritic membrane, whereas both heterotrimeric and homodimeric kinesin-2 motors function cooperatively in anterograde intraflagellar transport (IFT) and cilium biogenesis.
Sperm flagellar protein 2 is a protein that in humans is encoded by the SPEF2 gene.
Intraflagellar transport protein 81 homolog is a protein that in humans is encoded by the IFT81 gene. Together with IFT74/72 it forms a core complex to build IFT particles which are required for cilium formation. Additionally, it interacts with basal body components as CEP170 which regulates the disassembly of the cilium.
Intraflagellar transport protein 80 homolog (IFT80), also known as WD repeat-containing protein 56, is a protein that in humans is encoded by the IFT80 gene.
Sensenbrenner syndrome is a rare multisystem disease first described by Judith A. Sensenbrenner in 1975. It is inherited in an autosomal recessive fashion, and a number of genes appear to be responsible. Three genes responsible have been identified: intraflagellar transport (IFT)122 (WDR10), IFT43—a subunit of the IFT complex A machinery of primary cilia, and WDR35
Ciliogenesis is defined as the building of the cell's antenna or extracellular fluid mediation mechanism. It includes the assembly and disassembly of the cilia during the cell cycle. Cilia are important organelles of cells and are involved in numerous activities such as cell signaling, processing developmental signals, and directing the flow of fluids such as mucus over and around cells. Due to the importance of these cell processes, defects in ciliogenesis can lead to numerous human diseases related to non-functioning cilia. Ciliogenesis may also play a role in the development of left/right handedness in humans.
Giantin or Golgin subfamily B member 1 is a protein that in humans is encoded by the GOLGB1 gene. Giantin is located at the cis-medial rims of the Golgi apparatus and is part of the Golgi matrix that is responsible for membrane trafficking in secretory pathway of proteins. This function is key for proper localisation of proteins at the plasma membrane and outside the cell which is important for cell function that is dependent on for example receptors and the extracellular matrix function. Recent animal model knockout studies of GOLGB1 in mice, rat, and zebrafish have shown that phenotypes are different between species ranging from mild to severe craniofacial defects in the rodent models to just minor size defects in zebrafish. However, in adult zebrafish a tumoral calcinosis-like phenotype was observed, and in humans such phenotype has been linked to defective glycosyltransferase function.
