MYO3B
MYO3B encodes myosin IIIB, a class III actin-based motor with an amino-terminal kinase domain and retinal expression[1]. Mechanistically, MYO3B reaches actin protrusion tips through espin-1 (ESPN1) cargo and promotes filopodia elongation in COS7 models[2]. In sensory systems, MYO3A and MYO3B shape auditory hair bundles by limiting microvilli and stereocilia growth during cochlear development[3]. MYO3B and related class III motors also influence stereocilia-staircase spacing through espin-1 and espin-like cargos[4]. In mouse retina, Myo3B variants appear early in development, localize with Myo3A in photoreceptor inner segments, and show differential cone outer-segment distribution[5]. Compared with MYO3A, MYO3B lacks tail actin-binding activity, depends more strongly on cargo-mediated actin binding, and shows weaker actin-protrusion elongation activity in comparative assays[2][6]. Human MYO3A differs from MYO3B by an extended tail domain with an additional actin-binding motif, while MYO3A shows faster motor activity, higher ATPase activity, and stronger actin affinity[6]. No well-established MYO3B-specific agonist or inhibitor was supported by the retrieved peer-reviewed evidence.
References:
- [1]. Dosé AC, et al. A class III myosin expressed in the retina is a potential candidate for Bardet-Biedl syndrome. Genomics. 2002 May;79(5):621-4. [Content Brief]
- [2]. Merritt RC, et al. Myosin IIIB uses an actin-binding motif in its espin-1 cargo to reach the tips of actin protrusions. Curr Biol. 2012 Feb 21;22(4):320-5. [Content Brief]
- [3]. Lelli A, et al. Class III myosins shape the auditory hair bundles by limiting microvilli and stereocilia growth. J Cell Biol. 2016 Jan 18;212(2):231-44. [Content Brief]
- [4]. Ebrahim S, et al. Stereocilia-staircase spacing is influenced by myosin III motors and their cargos espin-1 and espin-like. Nat Commun. 2016 Mar 1;7:10833. [Content Brief]
- [5]. Katti C, et al. Cloning and distribution of myosin 3B in the mouse retina: differential distribution in cone outer segments. Exp Eye Res. 2009 Aug;89(2):224-37. [Content Brief]
- [6]. Raval MH, et al. Impact of the Motor and Tail Domains of Class III Myosins on Regulating the Formation and Elongation of Actin Protrusions. J Biol Chem. 2016 Oct 21;291(43):22781-22792. [Content Brief]
