Cooperative cargo transport by two molecular motors involves an elastic motor-motor coupling, which can reduce the motors' velocity and/or enhance their unbinding from the filament. We show theoretically that these interference effects lead, in general, to four distinct transport regimes. In addition to a weak coupling regime, kinesin and dynein motors are found to exhibit a strong coupling and an enhanced unbinding regime, whereas myosin motors are predicted to attain a reduced velocity regime. All of these regimes, which we derive by explicit calculations and general time scale arguments, can be explored experimentally by varying the elastic coupling strength.

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Abstract-Engineered constructs coupling a defined number of molecular motors provide an opportunity to study the cooperative transport of cargoes. Theoretical descriptions for the dynamics of such complexes can help to understand experimental data or to quantitatively formulate expectations for such experiments and provide a general framework for such analysis. Here, we review and extend recent theoretical studies that focused on pairs of molecular motors to study effects of coupling between the motors. We derive explicit results for two elastically coupled kinesin-1 motors as a function of the coupling strength using both linear and nonlinear springs. In addition, we discuss the general dynamics of such motor pairs, which is governed by characteristic time scales for the spontaneous unbinding of motors and for the built-up of strain forces that are sufficiently large to affect the run length and/or the velocity of the motors. We show how the comparison of these time scales can be used to predict the distinct behavior of different motor species, the effects of coupling, and the impact of the single motor velocity on the observable dynamics of a motor pair.

Adenovirus-mediated combination gene therapies have shown promising results in vaccination or treating malignant and genetic diseases. Nevertheless, an efficient system for the rapid assembly and incorporation of therapeutic genes into high-capacity adenoviral vectors (HCAdVs) is still missing. In this study, we developed the iMATCH (integrated modular assembly for therapeutic combination HCAdVs) platform, which enables the generation and production of HCAdVs encoding therapeutic combinations in high quantity and purity within 3 weeks. Our modular cloning system facilitates the efficient combination of up to four expression cassettes and the rapid integration into HCAdV genomes with defined sizes. Helper viruses (HVs) and purification protocols were optimized to produce HCAdVs with distinct capsid modifications and unprecedented purity (0.1 ppm HVs). The constitution of HCAdVs, with adapters for targeting and a shield of trimerized single-chain variable fragment (scFv) for reduced liver clearance, mediated cell- and organ-specific targeting of HCAdVs. As proof of concept, we show that a single HCAdV encoding an anti PD-1 antibody, interleukin (IL)-12, and IL-2 produced all proteins, and it led to tumor regression and prolonged survival in tumor models, comparable to a mixture of single payload HCAdVs in vitro and in vivo . Therefore, the iMATCH system provides a versatile platform for the generation of high-capacity gene therapy vectors with a high potential for clinical development.