Masaharu Terashima⁽¹⁾, Makoto Shimoyama⁽²⁾, Mikako Tsuchiya^{(3)
(1)(2)(3)}Department of Biochemistry. Shimane Medical University - Izumo. Japan

	[Biochemistry]	[Cell Biology & Cytology]

INTRODUCTION

Arginine-specific ADP-ribosylation is a post-translational modification, in which ADP-ribose moiety of NAD is transferred to the arginine residues in the target proteins. In eukaryotes, although arginine-specific ADP-ribosyltransferases (ADPRTs) have been detected in many species and tissues ⁽¹⁾, the functions of the transferases through the modification of the target proteins remain obscure.

We previously reported that the arginine-specific ADP-ribosyltransferase was present in the cytosol of chicken polymorphonuclear leukocytes (so-called heterophils) ⁽²⁾, and that the transferase could modify various isoforms of globular actin (G-actin) in vitro, thereby preventing the actin polymerization ⁽³⁾. ADP-ribosylation sites in skeletal muscle α-G-actin were determined to be Arg28 and Arg206, and the latter was proved to be crucial for actin polymerization and DNase I interaction ⁽⁴⁾. Moreover, an introduction of NAD into the heterophils inhibited the increase in filamentous actin contents induced by a chemotactic peptide formyl-methionyl-leucyl-phenylalanine ⁽⁵⁾. These results suggest that ADP-ribosylation of actin might regulate the cytoskeletal organization in vivo.

It is generally accepted that polymerization of actin and organization of the actin filaments are regulated by ATP hydrolysis and by numerous actin-binding proteins ⁽⁶⁾. Inhibitory effect of ADP-ribosylation on actin polymerization in vitro and in situ ^(3-5) may implicate additional mechanism to regulate cytoskeletal organization. Although we reported that filamentous actin (F-actin) was also ADP-ribosylated ⁽³⁾, we have not elucidated how ADP-ribosylation of F-actin affects its polymerization state. Thus, we turned our attention to see whether ADP-ribosylation of F-actin affects the actin polymerization or equilibrium state between G- and F-actins. In this study, we examined the influence of ADP-ribosylation on polymerization state of F-actin, and show here evidence that ADP-ribosylation of polymerized F-actin induces its depolymerization and increases G-actin contents.

Discussion Board

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[ABSTRACT] [INTRODUCTION] [MATERIAL & METHODS] [RESULTS AND DISCUSSION] [FIGURES] [ACKNOWLEDGEMENTS] [REFERENCES] [Discussion Board]

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	[Biochemistry]	[Cell Biology & Cytology]

Masaharu Terashima, Makoto Shimoyama, Mikako Tsuchiya
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Last update: 5/01/00