Isolation and Characterization of Secretory Actin . DNAase I Complex from Rat Pancreatic Juice

Abstract

DNAase I isolated from rat pancreatic juice was always found in association with a protein of molecular weight 43000. This association leads to inhibition of the isolated rat pancreatic DNAase I activity by 66%. The molecular weight of the complex was found to be 74000 by gel filtration indicating a 1 : 1 molar association of both proteins. Since the protein of molecular weight 43000 has a number of properties similar to skeletal muscle actin such as filament formation, nucleotide binding, inhibition of the rat pancreatic DNAase I activity and comigration with skeletal muscle actin on polyacrylamide gels in the presence of dodecylsulfate, it is concluded that DNAase I is bound to actin in rat pancreatic juice in a 1 : 1 complex. It is demonstrated that a protein fraction from bile is able to activate the DNAase I enzymatic activity of the rat secretory actin ‐ DNAase I complex.

Cleavage of actin by interleukin 1 beta-converting enzyme to reverse DNase I inhibition.

“…Full-length actin binds to and inhibits DNase I with an association constant of 109 M-1 (35), and actin-DNase complexes have been described in vivo (35,36), yet a physiological rationale for these observations has not been reported. If in healthy nonapoptosing cells one of the functions of actin is to inhibit DNase I, then it is conceivable that, at the onset of apoptosis, ICE may reverse this inhibition by cleaving actin into fragments that have a reduced capacity to inhibit the endonucleolytic activity of DNase I.…”

Detection of Deoxyribonuclease I Along the Secretory Pathway in Paneth Cells of Human Small Intestine

“…Actually, we found a number of blood cells and some Paneth cells contaminating the villous tip fragment under a light microscope. According to a number of previous reports, DNase I is secreted by exocrine glands, such as the pancreas and parotid gland, into the alimentary tract (Laskowski 1971;Rohr and Mannherz 1978;Lacks 1981). Furthermore, DNase I was also found to present in various tissues, including the kidney, lymph node, small intestine, heart, liver, and epididymis.…”

“…Deoxyribonuclease I (DNase I: EC.3.1.21.1), an endonuclease preferentially degrading double-stranded DNA, was first considered to be an exocrine pancreatic enzyme but was later found to be localized in a number of other tissues (Laskowski 1971;Rohr and Mannherz 1978;Lacks 1981;Polzar et al 1994;Zanotti et al 1995;Yao et al 1996). The enzymatic activity of DNase I is inhibited by monomeric (G) actin, which is present in all eukaryotic cells (Dabrowska et al 1949;Mannherz et al 1977).…”

The activation of actin:DNase I complex with rat liver plasma membranes

“…After formation of a stable 1: 1 complex the biological properties of both proteins are inhibited, i.e., the DNA degrading activity of DNase I and the ability of G-actin to form high molecular weight polymers. The isolation of a secretory actin:DNase I complex from rat pancreatic juice and the reversal of the inhibitory action of actin on DNase I by a protein from rat or human bile gives evidence for the natural occurrence of this complex and for a possible physiological importance [4]. The activating protein from bile has now been identified by us as 5'-nticleotidase (in preparation).…”