Melanophilin, a Myosin Va Adapter Protein, Biases Track Selection of Myosin Va-and Kinesin-1-Transported Liposomes at Actin-Microtubule Intersections In Vitro
- 1University of Vermont Larner College of Medicine
Abstract
In cells, myosin Va and kinesin-1 motors navigate their shared vesicular cargos through numerous actin-microtubule (MT) intersections. How cargos exit these intersections to ensure precise destination delivery remains unclear. We hypothesized that the myosin Va adapter melanophilin -- a phosphorylated protein that links myosin Va to melanosomes but can also bind actin and MTs -- acts as a phosphorylation-dependent switch to bias the tug-of-war between cargo-bound myosin Va and kinesin-1 at actin-MT intersections. We modeled melanosome transport in vitro using 350-nm liposomes with ~5 each of surface-bound constitutively active myosin Va and kinesin-1, and ~5 full-length melanophilin with varying phosphorylation levels. Regardless of the track the liposome entered the actin-MT intersection on, phosphorylated melanophilin biased liposomes to exit on actin, whereas dephosphorylated melanophilin biased liposomes to exit on MTs. Consistent with this, phosphorylated melanophilin preferentially bound actin 2-fold over MTs, and slowed myosin Va liposome transport on actin by ~40%, effectively acting as an anchor. Conversely, dephosphorylated melanophilin preferentially bound (2-fold) MTs over actin, and increased kinesin-1 liposome transport distance on MTs by acting as a tether. Therefore, melanophilin, depending on its phosphorylation state, biases track selection by kinesin-1/myosin Va transported cargos in actin-MT intersections that exist in complex cellular cytoskeletal networks.
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BibTeX
@misc{bensel2026melanophilin,
title = {{Melanophilin, a Myosin Va Adapter Protein, Biases Track Selection of Myosin Va-and Kinesin-1-Transported Liposomes at Actin-Microtubule Intersections In Vitro}},
author = {B. M. Bensel and P. M. Fagnant and J. E. Macfarlane and M. J. Previs and K. M. Trybus and D. M. Warshaw},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.01.748553},
url = {https://www.biorxiv.org/content/10.64898/2026.09.01.748553v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Melanophilin, a Myosin Va Adapter Protein, Biases Track Selection of Myosin Va-and Kinesin-1-Transported Liposomes at Actin-Microtubule Intersections In Vitro
AU - B. M. Bensel
AU - P. M. Fagnant
AU - J. E. Macfarlane
AU - M. J. Previs
AU - K. M. Trybus
AU - D. M. Warshaw
PY - 2026
DA - 2026/09/01
PB - bioRxiv
DO - 10.64898/2026.09.01.748553
UR - https://www.biorxiv.org/content/10.64898/2026.09.01.748553v1
AB - In cells, myosin Va and kinesin-1 motors navigate their shared vesicular cargos through numerous actin-microtubule (MT) intersections. How cargos exit these intersections to ensure precise destination delivery remains unclear. We hypothesized that the myosin Va adapter melanophilin -- a phosphorylated protein that links myosin Va to melanosomes but can also bind actin and MTs -- acts as a phosphorylation-dependent switch to bias the tug-of-war between cargo-bound myosin Va and kinesin-1 at actin-MT intersections. We modeled melanosome transport in vitro using 350-nm liposomes with ~5 each of surface-bound constitutively active myosin Va and kinesin-1, and ~5 full-length melanophilin with varying phosphorylation levels. Regardless of the track the liposome entered the actin-MT intersection on, phosphorylated melanophilin biased liposomes to exit on actin, whereas dephosphorylated melanophilin biased liposomes to exit on MTs. Consistent with this, phosphorylated melanophilin preferentially bound actin 2-fold over MTs, and slowed myosin Va liposome transport on actin by ~40%, effectively acting as an anchor. Conversely, dephosphorylated melanophilin preferentially bound (2-fold) MTs over actin, and increased kinesin-1 liposome transport distance on MTs by acting as a tether. Therefore, melanophilin, depending on its phosphorylation state, biases track selection by kinesin-1/myosin Va transported cargos in actin-MT intersections that exist in complex cellular cytoskeletal networks.
ER -