Composition and function of the C1b/C1f region in the ciliary central apparatus

Motile cilia are ultrastructurally complex cell organelles with the ability to actively move. The highly conserved central apparatus of motile 9 × 2 + 2 cilia is composed of two microtubules and several large microtubule-bound projections, including the C1b/C1f supercomplex. The composition and function of C1b/C1f subunits has only recently started to emerge. We show that in the model ciliate Tetrahymena thermophila, C1b/C1f contains several evolutionarily conserved proteins: Spef2A, Cfap69, Cfap246/LRGUK, Adgb/androglobin, and a ciliate-specific protein Tt170/TTHERM_00205170. Deletion of genes encoding either Spef2A or Cfap69 led to a loss of the entire C1b projection and resulted in an abnormal vortex motion of cilia. Loss of either Cfap246 or Adgb caused only minor alterations in ciliary motility. Comparative analyses of wild-type and C1b-deficient mutant ciliomes revealed that the levels of subunits forming the adjacent C2b projection but not C1d projection are greatly reduced, indicating that C1b stabilizes C2b. Moreover, the levels of several IFT and BBS proteins, HSP70, and enzymes that catalyze the final steps of the glycolytic pathway: enolase ENO1 and pyruvate kinase PYK1, are also reduced in the C1b-less mutants

Molecular chaperons: chaperones and chaperonins

Proteins must be folded into their correct three-dimensional conformation in order to attain biological function. Conversely, protein aggregation and misfolding are primary contributors to many devastating "conformational" diseases. Proteins are synthesized and folded continuously. The last of these processes is greatly assisted by molecular chaperones. They are a group of structurally diverse and mechanistically distinct proteins that either promote folding or prevent the aggregation of other proteins. Proteins that can be classified as molecular chaperones can be divided into two groups: (a) ribosome-associated chaperons responsible for co-traslational folding of polypetides and (b) cytoplasmic molecular chaperones including Hsp90, Hsp70/Hsp40 and chaperonin CCT in eukaryotic cells. Prokaryotic cells posses DnaK/DnaJ system and GroEL/GroES, respectively. This review focuses on the emerging role of molecular chaperones in protein quality control in eukaryotic and prokaryotic cells

Dimer βγ of G protein - signaling molecule

The extracellular signals received by receptors with seven membrane-spanning regions that activate the G proteins, are routed to several distinct intracellular pathways. The G proteins consist of two functional units, Gα subunit, that binds guanine nucleotides and Gβγ dimer that functions as a single unit. The regulation of signal transduction by the Gβγ complex at different protein interfaces: subunit - subunit, receptor - G protein, and Gβγ - effector, are reviewed. Gβγ dimer regulates over twelve cellular effectors including phospholipase-β, adenyl cyclases, ion channels and G-protein coupled receptor kinases, which control a broad range of cellular processes

Role of the Novel Hsp90 Co-Chaperones in Dynein Arms’ Preassembly

The outer and inner dynein arms (ODAs and IDAs) are composed of multiple subunits including dynein heavy chains possessing a motor domain. These complex structures are preassembled in the cytoplasm before being transported to the cilia. The molecular mechanism(s) controlling dynein arms’ preassembly is poorly understood. Recent evidence suggests that canonical R2TP complex, an Hsp-90 co-chaperone, in cooperation with dynein axonemal assembly factors (DNAAFs), plays a crucial role in the preassembly of ODAs and IDAs. Here, we have summarized recent data concerning the identification of novel chaperone complexes and their role in dynein arms’ preassembly and their association with primary cilia dyskinesia (PCD), a human genetic disorder

Effects of Roscovitine on Schedule of Divisional Morphogenesis, Basal Bodies Proliferation and Cell Divisions in Tetrahymena thermophila

Summary. During cell cycle of a ciliate Tetrahymena thermophila the divisions of micro- and macronucleus, cortical morphogenesis and ' cytokinesis are temporarily coordinated. Cortical morphogenesis begins with proliferation of the new ciliary basal bodies (BBs) within meridional cortical rows of ciliary BBs, and with the local proliferation of BBs, which form the new oral apparatus (OA2), positioned subequatorialy and destined for prospective posterior daughter cell (opisthe). Prior to cytokinesis, two prospective daughter cells are of equal size and show metamery of their cortical patterns. We studied effects of 20 uM roscovitine (an inhibitor of several cyclin-dependent kinases) on the cell cycle progression of T. thermophila. We showed that roscovitine delayed cell division, delayed or arrested macronuclear division and induced increase of cell size and the number of BBs in the cortical rows. The increase in the number of BBs in cortical rows induced cell elongation which was proportional to the increase in cell surface area. There was uncoupling between this BBs_proliferation which is continued during prolonged cell cycle and delayed cytokinesis, what resulted in topological alteration of the respective positions of the OA2 and of the contractile vacuole pores (CVPs). In roscovitine treated cells, the new OA2 was positioned subequatorialy, but the fission zone was shifted posterior to the equatorial plane of the cell and positioned across and in the extreme cases behind of the new OA2. This resulted in the formation of a large proter and small size opisthe. The roscovitine treatment induced a formation of a plethora of phenotypes of postdividing cells. We found that irrespective of changes in divisional morphogenesis induced by roscovitine treatment, all mature BBs were associated with the cdc!4-like phosphatase. Taken together all these data indicate that during cell cycle of T. thermophila the normal morphology of the daughter cells depends on the proper division of micro- and macronucleus and on temporal control of BBs proliferation along the longitudinal rows, during OA2 stomatogenesis and during selection of BBs involved in differentiation of apical BBs (couplets) and cell division. Key words: Tetrahymena, roscovitine, basal bodies, morphogenesis, macronucleus, cdc!4p. Addres

Tubulin Post-Translational Modifications and Microtubule Dynamics

Microtubules are hollow tube-like polymeric structures composed of α,β-tubulin heterodimers. They play an important role in numerous cellular processes, including intracellular transport, cell motility and segregation of the chromosomes during cell division. Moreover, microtubule doublets or triplets form a scaffold of a cilium, centriole and basal body, respectively. To perform such diverse functions microtubules have to differ in their properties. Post-translational modifications are one of the factors that affect the properties of the tubulin polymer. Here we focus on the direct and indirect effects of post-translational modifications of tubulin on microtubule dynamics