Optimal sidestepping of intraflagellar transport kinesins regulates structure and function of sensory cilia.

Cytoskeletal-based molecular motors produce force perpendicular to their direction of movement. However, it remains unknown whether and why motor proteins generate sidesteps movement along their filamentous tracks in vivo. Using Hessian structured illumination microscopy, we located green fluorescent protein (GFP)-labeled intraflagellar transport (IFT) particles inside sensory cilia of live Caenorhabditis elegans with 3-6-nanometer accuracy and 3.4-ms resolution. We found that IFT particles took sidesteps along axoneme microtubules, demonstrating that IFT motors generate torque in a living animal. Kinesin-II and OSM-3-kinesin collaboratively drive anterograde IFT. We showed that the deletion of kinesin-II, a torque-generating motor protein, reduced sidesteps, whereas the increase of neck flexibility of OSM-3-kinesin upregulated sidesteps. Either increase or decrease of sidesteps of IFT kinesins allowed ciliogenesis to the regular length, but changed IFT speeds, disrupted axonemal ninefold symmetry, and inhibited sensory cilia-dependent animal behaviors. Thus, an optimum level of IFT kinesin sidestepping is associated with the structural and functional fidelity of cilia.

Torque generation of kinesin motors is governed by the stability of the neck domain.

In long-range transport of cargo, prototypical kinesin-1 steps along a single protofilament on the microtubule, an astonishing behavior given the number of theoretically available binding sites on adjacent protofilaments. Using a laser trap assay, we analyzed the trajectories of several representatives from the kinesin-2 class on freely suspended microtubules. In stark contrast to kinesin-1, these motors display a wide range of left-handed spiraling around microtubules and thus generate torque during cargo transport. We provide direct evidence that kinesin's neck region determines the torque-generating properties. A model system based on kinesin-1 corroborates this result: disrupting the stability of the neck by inserting flexible peptide stretches resulted in pronounced left-handed spiraling. Mimicking neck stability by crosslinking significantly reduced the spiraling of the motor up to the point of protofilament tracking. Finally, we present a model that explains the physical basis of kinesin's spiraling around the microtubule.

Quality of life in breast cancer patients and surgical results of immediate tissue expander/implant-based breast reconstruction after mastectomy.

OBJECTIVES: The purpose of this study was to analyze the effects of prior radiotherapy (RT) as well as postmastectomy radiotherapy (PMRT) on patient-reported quality of life (QoL) and on surgical/aesthetic outcomes in patients with expander-/implant-based delayed immediate reconstruction (EIBR) compared to patients that underwent EIBR without any RT. MATERIAL AND METHODS: QoL was assessed by BREAST-Q, the surgical/aesthetic outcome by a structured examination and a picture analysis (BCCT.CORE software) and subsequently compared between the three cohorts. RESULTS: Of 161 eligible patients, 97 followed the invitation (no RT n = 54, 9 of them with bilateral EIBR; PMRT n = 26; history of RT n = 15). The surgical/aesthetic results were better in the RT-naive cohort than in the PMRT cohort, but satisfaction with outcome and psychosocial well-being were better in the PMRT cohort. The RT-naive cohort showed (significantly) higher scores in satisfaction with breast, satisfaction with implant and sexual well-being compared to the history of RT cohort, although satisfaction with outcome was comparable. The PMRT cohort reached significantly more points in almost all categories and better BCCT.CORE and examination results than the history of RT cohort. Of all patients, 92.7%, 84.6% and 78.6% (RT naive, PMRT, history of RT) would agree to undergo EIBR again. CONCLUSION: EIBR results in acceptable QoL and surgical results. In patients with a prior RT, QoL is significantly lower and surgical results are significantly worse. However, high acceptance rates suggest EIBR being a justifiable option even for this group. Prospective studies and long-term follow-up are required for definitive conclusions.

Regulation of a heterodimeric kinesin-2 through an unprocessive motor domain that is turned processive by its partner.

Cilia are microtubule-based protrusions of the plasma membrane found on most eukaryotic cells. Their assembly is mediated through the conserved intraflagellar transport mechanism. One class of motor proteins involved in intraflagellar transport, kinesin-2, is unique among kinesin motors in that some of its members are composed of two distinct polypeptides. However, the biological reason for heterodimerization has remained elusive. Here we provide several interdependent reasons for the heterodimerization of the kinesin-2 motor KLP11/KLP20 of Caenorhabditis elegans cilia. One motor domain is unprocessive as a homodimer, but heterodimerization with a processive partner generates processivity. The "unprocessive" subunit is kept in this partnership as it mediates an asymmetric autoregulation of the motor activity. Finally, heterodimerization is necessary to bind KAP1, the in vivo link between motor and cargo.