Desmin intermediate filaments and tubulin detyrosination stabilize growing microtubules in the cardiomyocyte

Abstract

In heart failure, an increased abundance of post-translationally detyrosinated microtubules stiffens the cardiomyocyte and impedes its contractile function. Detyrosination promotes interactions between microtubules, desmin intermediate filaments, and the sarcomere to increase cytoskeletal stiffness, yet the mechanism by which this occurs is unknown. We hypothesized that detyrosination may regulate the growth and shrinkage of dynamic microtubules to facilitate interactions with desmin and the sarcomere. Through a combination of biochemical assays and direct observation of growing microtubule plus-ends in adult cardiomyocytes, we find that desmin is required to stabilize growing microtubules at the level of the sarcomere Z-disk, where desmin also rescues shrinking microtubules from continued depolymerization. Further, reducing detyrosination (i.e. tyrosination) below basal levels promotes frequent depolymerization and less efficient growth of microtubules. This is concomitant with tyrosination promoting the interaction of microtubules with the depolymerizing protein complex of end-binding protein 1 (EB1) and CAP-Gly domain-containing linker protein 1 (CLIP1/CLIP170). The dynamic growth and shrinkage of tyrosinated microtubules reduce their opportunity for stabilizing interactions at the Z-disk region, coincident with tyrosination globally reducing microtubule stability. These data provide a model for how intermediate filaments and tubulin detyrosination establish long-lived and physically reinforced microtubules that stiffen the cardiomyocyte and inform both the mechanism of action and therapeutic index for strategies aimed at restoring tyrosination for the treatment of cardiac disease.

Decoding microtubule detyrosination: enzyme families, structures, and functional implications

“…kinesin 1 is preferably located on detyrosinated tubulin [52][53][54][55][56], but kinesin 3 preferentially localised to tyrosinated microtubules, important for transport of peripheral lysosomes [57][58][59]. Kinesin 5 [60], p150 [61][62][63], EB1 [64] and CAP-Gly domain containing linker protein (CLIP) 170 [64,65] also preferentially locate at tyrosinated microtubules. Desmin intermediate filaments [64,66] and vimentin (via kinesin) [67], as well as NADPH Oxidase (NOX) 2 [68,69], preferentially locate at detyrosinated microtubules.…”

“…Kinesin 5 [60], p150 [61][62][63], EB1 [64] and CAP-Gly domain containing linker protein (CLIP) 170 [64,65] also preferentially locate at tyrosinated microtubules. Desmin intermediate filaments [64,66] and vimentin (via kinesin) [67], as well as NADPH Oxidase (NOX) 2 [68,69], preferentially locate at detyrosinated microtubules. While the (de)tyrosination state of the microtubule can steer localisation of cellular factors, it is unclear how dysregulation of these molecular processes through disturbed detyrosination, contributes to the phenotypes of detyrosination or retyrosination deficient mice.…”

Nucleus Mechanosensing in Cardiomyocytes

“…Cytoskeletal variants can lead to broad responses in cellular dysfunction and structural alterations. Desmin variants have been associated with defective contractility mechanics and cellular remodeling [6,196,197]. Desmin knock-out has shown evidence of structural destabilization of the cytoskeleton and mitochondrial dysfunction in cardiomyocytes [198].…”

Myofibrillar malformations that arise in mdx muscle fibers are driven by detyrosinated microtubules

“…The structure and function of MTs are regulated by post-translational modifications (PTM) to their tubulin monomers. Detyrosination (deTyr), the reversible enzymatic removal of a-tubulin's COOH-terminal tyrosine, promotes the interaction of MTs with binding partners [12][13][14][15] . Work by our group has identified that MTs enriched in deTyr-tubulin (deTyr-MTs) regulate the stiffness of the muscle fiber cytoskeleton and thus the activation of NADPH Oxidase 2 (Nox2) dependent reactive oxygen species (ROS) and calcium (Ca 2+ ) signals by mechanotransduction 16,17 .…”