Dodding, M. | bioRxiv Science

bioRxiv2023

CryoET reveals actin filaments within platelet microtubules

Crosstalk between the actin and microtubule cytoskeletons is essential for many cellular processes. Recent studies have shown that microtubules and F-actin can assemble to form a composite structure where F-actin occupies the microtubule lumen. Whether these cytoskeletal hybrids exist in physiological settings and how they are formed is unclear. Here, we show that the short-crossover Class I actin filament previously identified inside microtubules in human HAP1 cells is cofilin-bound F-actin. Lumenal F-actin can be reconstituted in vitro, but cofilin is not essential. Moreover, actin filaments with both cofilin-bound and canonical morphologies reside within human platelet microtubules under physiological conditions. We propose that stress placed upon the microtubule network during motor-driven microtubule looping and sliding may facilitate the incorporation of actin into microtubules.

cell biology↗

bioRxiv2020

Mash-up design of a high-affinity peptide to highjack microtubule-based transport

Technologies that manipulate and augment the transport of vesicles and organelles by motor proteins along microtubules offer new routes to understanding its mechanistic basis, and could lead to therapeutics. Many cargoes for the kinesin-1 family of microtubule motors utilize adaptor proteins that harbor linear peptide motifs that are recognized by the tetratricopeptide repeats of kinesin light chains (KLCTPRs). These motifs bind with micromolar affinities at independent but overlapping sites. Here, we employ a fragment-linking peptide design strategy to generate an extended synthetic ligand (KinTag) with low nanomolar affinity for KLCTPRs. The X-ray crystal structure of the KLCTPR:KinTag complex demonstrates interactions as designed. Moreover, KinTag functions in cells to promote the transport of lysosomes with a high efficiency that correlates with its enhanced affinity. Together, these data demonstrate a new strategy for peptide design and its application to reveal that the more tightly a motor holds its cargo, the greater is the extent of cargo transport.

synthetic biology↗