Effects of post-translational modifications catalysed by pollen transglutaminase on the functional properties of microtubules and actin filaments

Abstract

TGases (transglutaminases) are a class of calcium-dependent enzymes that catalyse the interactions between acyl acceptor glutamyl residues and amine donors, potentially making crosslinks between proteins. To assess the activity of apple (Malus domestica) pollen TGase on the functional properties of actin and tubulin, TGase was prepared from apple pollen by hydrophobic interaction chromatography and assayed on actin and tubulin purified from the same cell type. The enzyme catalysed the incorporation of putrescine in the cytoskeleton monomers. When tested on actin filaments, pollen TGase induced the formation of high-molecular-mass aggregates of actin. Use of fluoresceincadaverine showed that the labelled polyamine was incorporated into actin by pollen TGase, similar to with guinea pig liver TGase. The pollen TGase also reduced the enzyme activity and the binding of myosin to TGase-treated actin filaments. Polymerization of tubulin in the presence of pollen TGase also yielded the formation of high molecular mass aggregates. Furthermore, the pollen TGase also affected the binding of kinesin to microtubules and reduced the motility of microtubules along kinesincoated slides. These results indicate that the pollen TGase can control different properties of the pollen tube cytoskeleton (including the ability of actin and tubulin to assemble and their interaction with motor proteins) and consequently regulate the development of pollen tubes.

Plasma Membrane Factor XIIIA Transglutaminase Activity Regulates Osteoblast Matrix Secretion and Deposition by Affecting Microtubule Dynamics

“…NC9 also reduces tubulin ‘clustering’ into patches on the plasma membrane and the fact that FXIIIA and it's crosslinking activity is found at sites where tubulin is associated with plasma membrane provides further evidence that such, covalent stabilization, indeed, occurs. Covalent tubulin crosslinking by TGs has been demonstrated before [92], [93] and, interestingly, incubation of monomeric tubulin with TG2 results in high molecular weight tubulin polymers in of 150–160 kDa – similar to what we observe in osteoblasts for Glu-tubulin [94]. The role of this 150 kDa Glu-tubulin can be only speculated at this point, but it may represent an additional stabilization step that could be required for the typical massive and directed COL I secretory process that occurs during in vitro bone formation where MTs may need to be ‘locked’ into place at plasma membrane transiently.…”

Senescence and programmed cell death in plants: polyamine action mediated by transglutaminase

“…These proteins are able to cross-link both actin and tubulin thereby generating a number of products with a higher molecular mass (from 90 to 160 kDa). An additional 55 kDa immunoreactive polypeptide of the cell wall fraction has the same molecular mass as an active TGase extracted from the Nicotiana petal cell wall as reported above (Del Duca et al, 2009; Di Sandro et al, 2010). …”

“…A further support for the role of TGase during the SI response comes from the discovery that cytoplasmic TGase of apple pollen is able to post-translationally modify actin and tubulin by conjugating with PAs (Del Duca et al, 1997). Such activity would result in the generation of high-molecular-weight aggregates (Del Duca et al, 2009) capable of altering the dynamic properties of the cytoskeletal filaments, of reducing the affinity of kinesin and myosin and, consequently, of affecting the dynamic activities based on the two motor proteins. Thus, TGase might actively participate in the SI response by playing a critical role in the reorganization of the cytoskeleton ( Figure 5A ).…”

Sensor potency of the moonlighting enzyme-decorated cytoskeleton: the cytoskeleton as a metabolic sensor

“…We cannot exclude the possibility that such interactions involve metabolic enzymes thereby taking cytoskeletal sensing to a very high level of integration. Some support for this possibility is given by the findings that (1) a fraction from tobacco pollen tubes containing PFK, homocysteine methyltransferase, pyruvate decarboxylase, and glucan protein synthase promoted the bundling of actin microfilaments and the interaction of these microfilaments with microtubules [34] and (2) in apple pollen, the binding of actin filaments to a transglutaminase (which catalyses the reaction between acyl acceptor glutamyl residues and amine donors) led to the aggregation of actin and to a similar aggregation using tubulin [35]. That said, the binding of metabolic enzymes to both microfilaments and MTs at the same time may be rare given that the binding of enzymes to the different cytoskeletal filaments is frequently isoform-specific and can vary with the activity state of the enzyme.…”