Extracellular actin in health and disease

Abstract

This review considers the functions of extracellular actin - cell surface bound, associated with extracellular matrix, or freely circulating. The role of this protein in different pathological processes is analyzed: its toxic effects and involvement in autoimmune diseases as an autoantigen. The extracellular actin clearance system and its role in protection against the negative effects of actin are characterized. Levels of free-circulating actin, anti-actin immunoglobulins, and components of the actin clearance system as prognostic biomarkers for different diseases are reviewed. Experimental approaches to protection against excessive amounts of free-circulating F-actin are discussed.

In-depth proteomic analyses of Haliotis laevigata (greenlip abalone) nacre and prismatic organic shell matrix

“…This was also shown to be the case with the shell of the brachiopod Magellania venosa [ 62 ], where we succeeded in significantly reducing the level of intracellular proteins when we treated powdered shell particles for 24 h with hypochlorite, but also lost some interesting proteins with some features characteristic of shell proteins, probably by removal of a large part of the extra-crystalline matrix. In mammals, intracellular proteins like the cytoskeletal component actin have been found at the cell surface, in extracellular matrices, and in body fluids (reviewed in [ 73 ]). The source of these proteins remains essentially unknown, but one suspected origin is from damaged or stressed cells.…”

Extracellular Actin Is a Receptor for Mycoplasma hyopneumoniae

“…105 proteins were identified that may be a target of M. hyopneumoniae surface proteins, including cytoskeleton-associated proteins such as myosin, keratin, vimentin, and most notably for this work, actin. Actin has been found on the surface of a wide range of eukaryote cells (Chen et al, 1978 ; Owen et al, 1978 ; Jones et al, 1979 ; Bachvaroff et al, 1980 ; Rubin et al, 1982 ; Sanders and Craig, 1983 ; Rosenblatt et al, 1985b ; Bach et al, 1986 ; Pardridge et al, 1989 ; Por et al, 1991 ; Moroianu et al, 1993 ; Dudani and Ganz, 1996 ; Smalheiser, 1996 ; Miles et al, 2006 ; Sandiford et al, 2015 ; Fu et al, 2017 ; Sudakov et al, 2017 ) and is a major constituent of the bronchoalveolar lavage fluid and airway surface liquid that bathes the porcine respiratory epithelium (Bartlett et al, 2013 ). Collectively, these observations indicate that extracellular actin may be an important receptor for M. hyopneumoniae .…”

“…One such receptor that is of particular interest is the major cytoskeletal protein actin that has been shown to be bound by several bacterial pathogens such as group B streptococcus, Mycoplasma suis , and Legionella pneumophila (Boone and Tyrrell, 2012 ; Bugalhão et al, 2015 ; Zhang et al, 2015 ). Actin is potentially underappreciated as a bacterial receptor and is reported to be expressed on the surface of a wide range of eukaryote cells (Chen et al, 1978 ; Owen et al, 1978 ; Jones et al, 1979 ; Sanders and Craig, 1983 ; Rosenblatt et al, 1985a ; Bach et al, 1986 ; Pardridge et al, 1989 ; Por et al, 1991 ; Dudani and Ganz, 1996 ; Smalheiser, 1996 ; Miles et al, 2006 ; Sandiford et al, 2015 ; Fu et al, 2017 ; Sudakov et al, 2017 ). Studies that seek to investigate the ability of M. hyopneumoniae to bind to actin have not been undertaken.…”

Rearrangement of Actin Microfilaments in the Development of Olfactory Receptor Cells in Fish

“…The most dynamic cytoskeletal component is the system of actin microfilaments. These filaments have been shown to play a crucial role in cell migration, in the elongation of cell processes, in the transport of organelles and macromolecules, and in the lateral movement and regrouping of adhesion molecules and plasma membrane receptors 7 – 10 . There are no reports in the literature on the possible involvement of actin in the development, migration, and subsequent differentiation of OSNs.…”