Lung optimized treatment with CyberKnife® in inoperable lung cancer patients: feasibility analysis of a mono-institutional 115 patient series.

CyberKnife® Lung Optimized Treatment (LOT) allows the treatment of lung cancer without invasive fiducial implantation. The aim of this retrospective analysis was to evaluate the feasibility, toxicity and clinical outcome. One hundred fifteen patients (124 lesions) were treated with CyberKnife® using LOT. The median age was 72.6 years (range 31.8-90.3). From 124 treated lesions, 52 were with histopathological confirmation (41 primitive pulmonary cancers, 8 pulmonary metastases) and 72 as untyped tumors. For 5 patients (6 lesions) treatment was an in-field re-irradiation. Concomitant therapy was administered in 7 patients. Zero-View tracking was applied in 69 patients, 1-View in 33 patients, 2-View in 22 patients. The median total dose was 45 Gy (range 18-54), median dose/fraction was 15 Gy (range 4-18) with a median prescription isodose of 80% (range 68-85). The median planning target volume (PTV) was 25 cm3 (range 3-195). The median follow-up was 20 months (range 7-47). Thirty-seven patients (32%) were alive with no evidence of disease, 39 patients (34%) were alive with clinically evident disease, and 38 patients (33%) died of the disease. The 1- and 2-year overall survival (OS) rate was 83% and 61%. The median time to progression was 19 months (95% confidence interval: 11-19 months), 1- and 2-year progression-free survival (PFS) rates were 62% and 41%, respectively. Smaller PTV was significantly associated with better OS, PFS and in-field PFS in univariate and multivariate analyses. Acute toxicity was observed in 36 patients (41%). Late toxicity was registered in 25 patients (29%). G3 late toxicity was observed in one patient (1.1%). Our data suggest that fiducial less-stereotactic body radiation therapy (SBRT) is a feasible, well-tolerated and potentially effective treatment with high compliance in the setting of inoperable patients due to concomitant disease or previous treatments.

Recombinant AAV-mediated in vivo long-term expression and antitumour activity of an anti-ganglioside GM3(Neu5Gc) antibody.

The ganglioside GM3(Neu5Gc) has gained increasing attention as therapeutic target because of its selective expression in various human tumours, such as melanoma, breast and lung cancer. 14F7 is a mouse IgG1 with specific reactivity to GM3(Neu5Gc)-positive tumours. The therapeutic activity of 14F7 has also been demonstrated in vivo, through its repetitive passive administration in tumour-bearing animals. In this work we used an alternative strategy to deliver recombinant 14F7 in vivo and analysed the therapeutic efficacy of this approach. We engineered a recombinant adeno-associated vector to direct the expression of secretable recombinant 14F7 in BALB/c animals. A single administration of the rAAV induced efficient production and secretion of the antibody in the bloodstream, with an expression level reaching plateau at ∼3 weeks after injection and persisting for almost a year. Strikingly, upon challenge with GM3(Neu5Gc)-positive X63-AG8.653 myeloma cells, tumour development was significantly delayed in animals treated with rAAV-14F7 with respect to animals treated with a control rAAV codifying for an irrelevant antibody. Finally, no significant differences in survival proportion were detected in animals injected with rAAV-14F7 or treated by standard administration of repetitive doses of purified monoclonal antibody 14F7.

High-dose chemotherapy in relapsed or refractory Hodgkin lymphoma patients: a reappraisal of prognostic factors.

High-dose chemotherapy (HDCT) has a consolidated role in the treatment of patients with refractory or relapsed Hodgkin lymphoma (HL). We report clinical results of 97 HL patients who underwent HDCT for refractory (62 patients) or relapsed (35 patients) diseases in Istituto Europeo di Oncologia, from 1995 to 2009. Treatment included high-dose carmustine, etoposide, cytarabine and melphalan in 84 patients and high-dose idarubicin and melphalan in 13 patients with subsequent peripheral hemopoietic stem cells transplant. Outcomes were evaluated in terms of progression-free survival (PFS) and overall survival (OS). In order to identify prognostic factors for outcome, a multivariate analysis for age, sex, disease status (refractory/relapsed), disease stage, B symptoms, presence of extranodal involvement, bulky disease, elevated lactate dehydrogenase, number of previous chemotherapy lines, remission status before transplant, 18F-fluoro-deoxy-d-glucose positron emission tomography ((18) FDG-PET) status before and after transplant was done. A clinical response was achieved in 91% of patients, with complete remissions in 76/97 patients. With a median follow-up of 45 months (range 1-164 months), 5-year PFS and OS were 64% and 71%, respectively. Remission status after induction therapy, 18F-fluoro-deoxy-d-glucose positron emission tomography status before and after transplant were the most important prognostic factors for PFS and OS in univariate or multivariate analyses. HDCT is able to induce a high remission rate and a prolonged PFS in more than 50% of the patients with refractory and relapsed HL.

Phantom study of stereotactic radioablation for ventricular tachycardia (STRA-MI-VT) using Cyberknife Synchrony Respiratory Tracking System with a single fiducial marker.

PURPOSE: Within the STRA-MI-VT phase Ib/II trial (NCT04066517), the aim of this phantom study was to explore the feasibility of Cyberknife treatments on cardiac lesions by tracking as a single marker the lead tip of an implantable cardioverter defibrillator. The residual displacement of the lesion during the tracking was studied, planning margins were found and the dosimetric accuracy of the treatment was checked. MATERIALS AND METHODS: A lead was inserted into a phantom (EasyCube phantom, Sun Nuclear Co, USA) and then placed on the translating ExacTrac Gating System (BrainLAB AG, Germany). The phantom was rotated, a virtual lesion was identified and its displacement during the tracking was studied. Two plans were compared, calculated on the unrotated volume and on the envelope of the unrotated and the rotated volumes. The plans were delivered using the Cyberknife System (Accuray Inc, USA) and their dosimetric accuracy verified by gamma analysis with gafchromic films. RESULTS: The residual margin increases enhancing the distance between the lead and the lesion. It is 4 mm for distance 0 cm and 5 mm for distance 5 cm. The coverage is reduced by 3.8% (interquartile range 2.5%-4.7%) when the dose is prescribed on the unrotated volume. All treatment plans are accurate and 3% 3 mm gamma analysis results are greater than 94%. CONCLUSIONS: Results showed that tracking with a single marker is feasible considering adequate residual planning margins. The volumes could be further reduced by using additional markers, for example by placing them on the patient's skin.

High prevalence of latent tuberculosis infection in autoimmune disorders such as psoriasis and in chronic respiratory diseases, including lung cancer.

The early diagnosis and treatment of individuals harboring M. tuberculosis is key to ensuring the effectiveness of health programs aimed at the elimination of tuberculosis (TB). Monitoring for TB also has other important health care implications for the related immune pathology caused by the chronic inflammatory response to M. tuberculosis. Moreover, the recent introduction of biologic therapies for the treatment of several immune-mediated inflammatory diseases has shown unexpected high frequencies of reactivation of latent TB. The present cross-sectional study is aimed at estimating the prevalence of latent tuberculosis infection (LTBI) in different groups of subjects, either undergoing a routine program of screening for TB or a clinical monitoring of autoimmune or lung disorders, by analyzing their immune response in vitro to a pool of different M. tuberculosis antigens through an IFN-gamma-release assay (IGRA). We consecutively tested 1,644 subjects including health care workers (931), healthy immigrants from different countries (93), patients with a diagnosis of psoriasis (405), patients with lung inflammatory disease (60) or lung neoplasia (32) and a group of HIV-1 infected Italian subjects (120). The prevalence of IGRAs positive responses among health care workers was 8.9 percent. In comparison, significantly higher frequencies were found in healthy immigrant subjects (33.3%), similar to those found in inflammatory broncho-pneumopathies (34.5%) or lung cancer (29.6%). Interestingly, an unexpected high prevalence was also found in patients affected by psoriasis (18.0%), while HIV-infected subjects had values comparable to those of health care workers (10.8%). An age cut-off was determined and applied for each group by receiver operating characteristic (ROC) curves in order to perform the statistical analysis among age-comparable groups. Multivariate analysis showed that the age and clinical conditions such as having a diagnosis of psoriasis or a lung inflammatory disease were independent risk factors for developing an IGRA positive response. This study highlights an unprecedented high prevalence of IGRA positive responses among patients affected by psoriasis and emphasizes the need for a preliminary assessment of LTBI before the administration of any biologic therapy based on cytokine antagonists such as anti-TNF-alpha. Moreover, screening for LTBI should be routinely performed in the presence of a chronic pulmonary disease.

STRA-MI-VT (STereotactic RadioAblation by Multimodal Imaging for Ventricular Tachycardia): rationale and design of an Italian experimental prospective study.

BACKGROUND: Ventricular tachycardia (VT) is a life-threatening condition, which usually implies the need of an implantable cardioverter defibrillator in combination with antiarrhythmic drugs and catheter ablation. Stereotactic body radiotherapy (SBRT) represents a common form of therapy in oncology, which has emerged as a well-tolerated and promising alternative option for the treatment of refractory VT in patients with structural heart disease. OBJECTIVE: In the STRA-MI-VT trial, we will investigate as primary endpoints safety and efficacy of SBRT for the treatment of recurrent VT in patients not eligible for catheter ablation. Secondary aim will be to evaluate SBRT effects on global mortality, changes in heart function, and in the quality of life during follow-up. METHODS: This is a spontaneous, prospective, experimental (phase Ib/II), open-label study (NCT04066517); 15 patients with structural heart disease and intractable VT will be enrolled within a 2-year period. Advanced multimodal cardiac imaging preceding chest CT-simulation will serve to elaborate the treatment plan on different linear accelerators with target and organs-at-risk definition. SBRT will consist in a single radioablation session of 25 Gy. Follow-up will last up to 12 months. CONCLUSIONS: We test the hypothesis that SBRT reduces the VT burden in a safe and effective way, leading to an improvement in quality of life and survival. If the results will be favorable, radioablation will turn into a potential alternative option for selected patients with an indication to VT ablation, based on the opportunity to treat ventricular arrhythmogenic substrates in a convenient and less-invasive manner.

Monoclonal antibodies to dynein subunits reveal the existence of cytoplasmic antigens in sea urchin egg.

Monoclonal antibodies directed against subunits of a sea urchin flagellar dynein were used to test for the presence of cytoplasmic antigens in preparations of fertilized eggs and mitotic apparati . A 9-10 S complex composed of 330,000-, 134,000-, and 126,000-mol-wt subunits was isolated from outer arms of Strongylocentrotus purpuratus sperm flagella and used to characterize the antibodies. Seven monospecific antibodies to the 330,000 subunit and two against the 134,000 subunit of the 9-10 S complex were identified by binding to nitrocellulose blots of electrophoretograms resolving polypeptides from different dynein preparations. The antibodies were applied also to blots of polypeptides from fertilized sea urchin egg at the first metaphase and a cellular fraction of mitotic apparati . Three of the antibodies to the 330,000 subunit bound to a cytoplasmic polypeptide of approximately the same molecular weight and the two antibodies to the smaller subunits recognized a polypeptide of 124,000 apparent molecular weight. Both antigens appeared to be enriched in the fraction containing mitotic apparati . These results indicate that polypeptides similar to two subunits of the 9-10 S complex are present in eggs at metaphase, and they are apparently associated with the mitotic apparatus.

Isolation of a sixth dynein subunit adenosine triphosphatase of Chlamydomonas axonemes.

This study of the axoneme led to the identification of a previously unknown adenosine triphosphatase (ATPase), which is likely a major component of inner dynein arms. The ATPase was isolated from a soluble fraction of axonemes obtained from pf 28, a Chlamydomonas mutant lacking the outer dynein arms. The activity hydrolyzed up to 2.3 mumol of ATP.min-1.mg-1 of protein (at pH 7.2, in the presence of both Ca++ and Mg++), had a sedimentation coefficient of 11S in sucrose gradient, and cosedimented with four polypeptides of apparent molecular weight 325,000, 315,000 140,000, and 42,000. Several arguments indicate that the new ATPase is a component of the inner dynein arms. Three or four polypeptides cosedimenting with the activity belong to a group of axonemal components that are deficient in the axonemes of pf 23 and pf 30, two mutants that display different levels of inner dynein arm deficiency. The 42,000 component is axonemal actin, a subunit of two other inner dynein ATPases. The two polypeptides of molecular weight greater than 300,000 have electrophoretic mobility similar to that of high molecular weight components of outer and inner dynein arms. In spite of some similarities each ATPase isolated from inner or outer arms is composed of a different set of polypeptides. Different ATPases may be required for the modulation of localized sliding of adjacent outer double microtubules in the axoneme.

Monoclonal antibodies specific for an acetylated form of alpha-tubulin recognize the antigen in cilia and flagella from a variety of organisms.

Seven monoclonal antibodies raised against tubulin from the axonemes of sea urchin sperm flagella recognize an acetylated form of alpha-tubulin present in the axoneme of a variety of organisms. The antigen was not detected among soluble, cytoplasmic alpha-tubulin isoforms from a variety of cells. The specificity of the antibodies was determined by in vitro acetylation of sea urchin and Chlamydomonas cytoplasmic tubulins in crude extracts. Of all the acetylated polypeptides in the extracts, only alpha-tubulin became antigenic. Among Chlamydomonas tubulin isoforms, the antibodies recognize only the axonemal alpha-tubulin isoform acetylated in vivo on the epsilon-amino group of lysine(s) (L'Hernault, S.W., and J.L. Rosenbaum, 1985, Biochemistry, 24:473-478). The antibodies do not recognize unmodified axonemal alpha-tubulin, unassembled alpha-tubulin present in a flagellar matrix-plus-membrane fraction, or soluble, cytoplasmic alpha-tubulin from Chlamydomonas cell bodies. The antigen was found in protein fractions that contained axonemal microtubules from a variety of sources, including cilia from sea urchin blastulae and Tetrahymena, sperm and testis from Drosophila, and human sperm. In contrast, the antigen was not detected in preparations of soluble, cytoplasmic tubulin, which would not have contained tubulin from stable microtubule arrays such as centrioles, from unfertilized sea urchin eggs, Drosophila embryos, and HeLa cells. Although the acetylated alpha-tubulin recognized by the antibodies is present in axonemes from a variety of sources and may be necessary for axoneme formation, it is not found exclusively in any one subset of morphologically distinct axonemal microtubules. The antigen was found in similar proportions in fractions from sea urchin sperm axonemes enriched for central pair or outer doublet B or outer doublet A microtubules. Therefore the acetylation of alpha-tubulin does not provide the mechanism that specifies the structure of any one class of axonemal microtubules. Preliminary evidence indicates that acetylated alpha-tubulin is not restricted to the axoneme. The antibodies described in this report may allow us to deduce the role of tubulin acetylation in the structure and function of microtubules in vivo.

Cytoplasmic microtubules containing acetylated alpha-tubulin in Chlamydomonas reinhardtii: spatial arrangement and properties.

A monoclonal antibody, 6-11B-1, specific for acetylated alpha-tubulin (Piperno, G., and M. T. Fuller, 1985, J. Cell Biol., 101:2085-2094) was used to study the distribution of this molecule in interphase cells of Chlamydomonas reinhardtii. Double-label immunofluorescence was performed using 6-11B-1, and 3A5, an antibody specific for all alpha-tubulin isoforms. It was found that acetylated alpha-tubulin is not restricted to the axonemes, but is also present in basal bodies and in a subset of cytoplasmic microtubules that radiate from the basal bodies just beneath the plasma membrane. Immunoblotting experiments of basal body polypeptide components using 6-11B-1 as a probe confirmed that basal bodies contain acetylated alpha-tubulin. In the cell body, 6-11B-1 stained an average of 2.2 microtubules/cell, while 3A5 stained an average of 6.5 microtubules. Although exposure to 0 degrees C depolymerized both types of cytoplasmic microtubules, exposure to various concentrations of colchicine or nocodazole showed that the acetylated microtubules are much more resistant to drug-induced depolymerization than nonacetylated microtubules. Axonemes and basal bodies are already known to be colchicine-resistant. All acetylated microtubules appear, therefore, to be more drug-resistant than nonacetylated microtubules. The acetylation of alpha-tubulin may be part of a mechanism that stabilizes microtubules.

The proximal portion of Chlamydomonas flagella contains a distinct set of inner dynein arms.

A specific type of inner dynein arm is located primarily or exclusively in the proximal portion of Chlamydomonas flagella. This dynein is absent from flagella less than 6 microns long, is assembled during the second half of flagellar regeneration time and is resistant to extraction under conditions causing complete solubilization of two inner arm heavy chains and partial solubilization of three other heavy chains. This and other evidence described in this report suggest that the inner arm row is composed of five distinct types of dynein arms. Therefore, the units of three inner arms that repeat every 96 nm along the axoneme are composed of different dyneins in the proximal and distal portions of flagella.

Cross-reactivity of antibodies specific for flagellar tektin and intermediate filament subunits.

Monoclonal antibodies specific for each of the flagellar tektins were prepared and used to determine whether structures similar to tektin filaments are present in cells lacking cilia or flagella. This analysis was performed by double-label immunofluorescence microscopy of several cell lines and by immunoblots of protein fractions. Two of the four anti-tektin antibodies, the antibodies 3-7-1 and 3-10-1, which bind different epitopes of the C-tektin, label 3T3, HeLa, PtK2, and BHK-21 cells as well as myotubes. The antibody 3-7-1 stains intermediate filament structures in the cells and binds vimentin or desmin in preparations of cytoskeletal proteins; whereas the antibody 3-10-1 stains nuclear envelopes in the cells and binds lamin A and C in preparations of cytoskeletal proteins or nuclear lamina. Structural similarities between the C-tektin and intermediate filament proteins probably are extended to more than two epitopes because polyclonal antibodies anti-vimentin and anti-desmin bind to C-tektin. These polyclonal antibodies also bind to A-tektin. The cross-reaction of monoclonal and polyclonal antibodies binding to epitopes in tektin and intermediate filament components and the existence of a high content of alpha-helical structure in the tektin subunits (Linck, R. W., and G. L. Langevin, 1982, J. Cell Sci., 58:1-22) indicate that tektin and intermediate filaments are homologous in several parts of their structure.

The inner dynein arms I2 interact with a "dynein regulatory complex" in Chlamydomonas flagella.

We provide indirect evidence that six axonemal proteins here referred to as "dynein regulatory complex" (drc) are located in close proximity with the inner dynein arms I2 and I3. Subsets of drc subunits are missing from five second-site suppressors, pf2, pf3, suppf3, suppf4, and suppf5, that restore flagellar motility but not radial spoke structure of radial spoke mutants. The absence of drc components is correlated with a deficiency of all four heavy chains of inner arms I2 and I3 from axonemes of suppressors pf2, pf3, suppf3, and suppf5. Similarly, inner arm subunits actin, p28, and caltractin/centrin, or subsets of them, are deficient in pf2, pf3, and suppf5. Recombinant strains carrying one of the mutations pf2, pf3, or suppf5 and the inner arm mutation ida4 are more defective for I2 inner arm heavy chains than the parent strains. This evidence indicates that at least one subunit of the drc affects the assembly of and interacts with the inner arms I2.

Mutations in the "dynein regulatory complex" alter the ATP-insensitive binding sites for inner arm dyneins in Chlamydomonas axonemes.

To understand mechanisms of regulation of dynein activity along and around the axoneme we further characterized the "dynein regulatory complex" (drc). The lack of some axonemal proteins, which together are referred to as drc, causes the suppression of flagellar paralysis of radial spoke and central pair mutants. The drc is also an adapter involved in the ATP-insensitive binding of I2 and I3 inner dynein arms to doublet microtubules. Evidence supporting these conclusions was obtained through analyses of five drc mutants: pf2, pf3, suppf3, suppf4, and suppf5. Axonemes from drc mutants lack part of I2 and I3 inner dynein arms as well as subsets of seven drc components (apparent molecular weight from 29,000 to 192,000). In the absence of ATP-Mg, dynein-depleted axonemes from the same mutants bind I2 and I3 inner arms at both ATP-sensitive and -insensitive sites. At ATP-insensitive sites, they bind I2 and I3 inner arms to an extent that depends on the drc defect. This evidence suggested to us that the drc forms one binding site for the I2 and I3 inner arms on the A part of doublet microtubules.

Posttranslational modifications of alpha tubulin: detyrosination and acetylation differentiate populations of interphase microtubules in cultured cells.

Subsets of microtubules enriched in posttranslationally detyrosinated (Gundersen, G. G., M. H. Kalnoski, and J. C. Bulinski. 1984. Cell. 38:779) or acetylated (Piperno, G., M. Le Dizet, and X. Chang. 1987. J. Cell Biol. 104:298), alpha tubulin have previously been described in interphase cultured cells. In this study an immunofluorescence comparison of these minor populations of microtubules revealed that, in African green monkey kidney epithelial cells (TC-7 line), the population of microtubules enriched in detyrosinated tubulin was virtually coincident with the population enriched in acetylated alpha tubulin. In some cell types, however, such as human HeLa or marsupial PtK-2 cells, only one posttranslationally modified form of tubulin, i.e., acetylated or detyrosinated, respectively, was detectable in microtubules. In TC-7 cells, although both modifications were present, dissimilar patterns and kinetics of reappearance of microtubules enriched in detyrosinated and acetylated tubulin were observed after recovery of cells from microtubule-depolymerizing treatments or from mitosis. Thus, a minor population of microtubules exists in cultured cells that contains an elevated level of tubulin modified in either one or two ways. While these two modifications occur primarily on the same subset of microtubules, they differ in their patterns of formation in vivo.

Inner dynein arms but not outer dynein arms require the activity of kinesin homologue protein KHP1(FLA10) to reach the distal part of flagella in Chlamydomonas.

Inner dynein arms, but not outer dynein arms, require the activity of KHP1(FLA10) to reach the distal part of axonemes before binding to outer doublet microtubules. We have analyzed the rescue of inner or outer dynein arms in quadriflagellate dikaryons by immunofluorescence microscopy of p28(IDA4), an inner dynein arm light chain, or IC69(ODA6), an outer dynein arm intermediate chain. In dikaryons two strains with different genetic backgrounds share the cytoplasm. As a consequence, wild-type axonemal precursors are transported to and assembled in mutant axonemes to complement the defects. The rescue of inner dynein arms containing p28 in ida4-wild-type dikaryons progressively occurred from the distal part of the axonemes and with time was extended towards the proximal part. In contrast, the rescue of outer dynein arms in oda2-wild-type dikaryons progressively occurred along the entire length of the axoneme. Rescue of inner dynein arms containing p28 in ida4fla10-fla10 dikaryons was similar to the rescue observed in ida4-wild-type dikaryons at 21 degrees C, whereas it was inhibited at 32 degrees C, a nonpermissive temperature for KHP1(FLA10). In contrast, rescue of outer dynein arms in oda2fla10-fla10 dikaryons was similar to the rescue observed in oda2-wild-type dikaryons at both 21 degrees and 32 degrees C and was not inhibited at 32 degrees C. Positioning of substructures in the internal part of the axonemal shaft requires the activity of kinesin homologue protein 1.

Microtubules containing acetylated alpha-tubulin in mammalian cells in culture.

The subcellular distribution of microtubules containing acetylated alpha-tubulin in mammalian cells in culture was analyzed with 6-11B-1, a monoclonal antibody specific for acetylated alpha-tubulin. Cultures of 3T3, HeLa, and PtK2 cells were grown on coverslips and observed by immunofluorescence microscopy after double-staining by 6-11B-1 and B-5-1-2, a monoclonal antibody specific for all alpha-tubulins. The antibody 6-11B-1 binds to primary cilia, centrioles, mitotic spindles, midbodies, and to subsets of cytoplasmic microtubules in 3T3 and HeLa cells, but not in PtK2 cells. These observations confirm that the acetylation of alpha-tubulin is a modification occurring in different microtubule structures and in a variety of eukaryotic cells. Some features of the acetylation of cytoplasmic microtubules of mammalian cells are also described here. First, acetylated alpha-tubulin is present in microtubules that, under depolymerizing conditions, are more stable than the majority of cytoplasmic microtubules. In addition to the specific microtubule frameworks already mentioned, cytoplasmic microtubules resistant to nocodazole or colchicine, but not cold-resistant microtubules, contain more acetylated alpha-tubulin than the rest of cellular microtubules. Second, the alpha-tubulin in all cytoplasmic microtubules of 3T3 and HeLa cells becomes acetylated in the presence of taxol, a drug that stabilizes microtubules. Third, acetylation and deacetylation of cytoplasmic microtubules are reversible in cells released from exposure to 0 degrees C or antimitotic drugs. Fourth, the epitope recognized by the antibody 6-11B-1 is not absolutely necessary for cell growth and division. This epitope is absent in PtK2 cells. The acetylation of alpha-tubulin could regulate the presence of microtubules in specific intracellular spaces by selective stabilization.

Three distinct inner dynein arms in Chlamydomonas flagella: molecular composition and location in the axoneme.

The molecular composition and organization of the row of axonemal inner dynein arms were investigated by biochemical and electron microscopic analyses of Chlamydomonas wild-type and mutant axonemes. Three inner arm structures could be distinguished on the basis of their molecular composition and position in the axoneme as determined by analysis of pf30 and pf23 mutants. The three inner arm structures repeat every 96 nm and are referred to here as inner arms I1, I2, and I3. I1 is proximal to the radial spoke S1, whereas I2 and I3 are distal to spokes S1 and S2, respectively. The mutant pf30 lacks I1 whereas the mutant pf23 lacks both I1 and I2 but has a normal inner arm I3. Each of the six heavy chains that was identified as an inner dynein arm subunit has a site for ATP binding and hydrolysis. Two of the heavy chains together with a polypeptide of 140,000 molecular weight form the inner arm I1 and were extracted from the axoneme as a complex that had a sedimentation coefficient close to 21S at high ionic strength. Different subsets of two of the remaining four heavy chains form the inner arms I2 and I3. These arms at high ionic strength are dissociated as 11S particles that include one heavy chain, one intermediate chain, two light chains, and actin. These and other lines of evidence indicate that the inner arm I1 is different in structure and function from the inner arms I2 and I3.

Protein particles in Chlamydomonas flagella undergo a transport cycle consisting of four phases.

We used an improved procedure to analyze the intraflagellar transport (IFT) of protein particles in Chlamydomonas and found that the frequency of the particles, not only the velocity, changes at each end of the flagella. Thus, particles undergo structural remodeling at both flagellar locations. Therefore, we propose that the IFT consists of a cycle composed of at least four phases: phases II and IV, in which particles undergo anterograde and retrograde transport, respectively, and phases I and III, in which particles are remodeled/exchanged at the proximal and distal end of the flagellum, respectively. In support of our model, we also identified 13 distinct mutants of flagellar assembly (fla), each defective in one or two consecutive phases of the IFT cycle. The phase I-II mutant fla10-1 revealed that cytoplasmic dynein requires the function of kinesin II to participate in the cycle. Phase I and II mutants accumulate complex A, a particle component, near the basal bodies. In contrast, phase III and IV mutants accumulate complex B, a second particle component, in flagellar bulges. Thus, fla mutations affect the function of each complex at different phases of the cycle.

Radial spokes of Chlamydomonas flagella: genetic analysis of assembly and function.

In addition to the previously studied pf-14 and pf-1 loci in Chlamydomonas reinhardtii, mutations for another five genes (pf-17, pf-24, pf-25, pf-26, and pf-27) have been identified and characterized as specifically affecting the assembly and function of the flagellar radial spokes. Mutants for each of the newly identified loci show selective alterations for one or more of the 17 polypeptides in the molecular weight range of 20,000-130,000 which form the radial spoke structure. In specific instances the molecular defect has been correlated with altered radial spoke morphology. Biochemical analysis of in vivo complementation in mutant X wild-type dikaryons has provided indirect evidence that mutations for four of the five new loci (pf-17, pf-24, pf-25, and pf-26) reside in structural genes for spoke components. In the case of pf-24, the identity of the mutant gene product was supported by analysis of induced intragenic revertants. In contrast to the other radial spoke mutants thus far investigated, evidence suggests that the gene product in pf-27 is extrinsic to the radial spokes and is required for the specific in vivo phosphorylation of spoke polypeptides.