Abstract
MacMARCKS (also known as myristoylated alanine-rich protein kinase C substrate (MARCKS)-related protein) is a member of the MARCKS family of protein kinase C substrates. MacMARCKS contains within it a basic effector domain that contains the serine residues that are phosphorylated by protein kinase C, as well as a calcium/calmodulin and actin-binding site. Two previous reports demonstrated that a macrophage cell line expressing a mutant form of MacMARCKS that lacks the effector domain is defective in phagocytosis and cell adhesion (Zhu, Z., Bao, Z., and Li, J. (1995) J. Biol. Chem. 270, 17652-17655; Li, J., Zhu, Z., and Bao, Z. (1996) J. Biol. Chem. 271, 12985-12990). We report here that macrophages from MacMARCKS null mice phagocytose and spread normally. Thus, although MacMARCKS is recruited to phagosomes, it is not absolutely required for phagocytosis.
Highlights
MacMARCKS ( known as myristoylated alaninerich protein kinase C substrate (MARCKS)-related protein) is a member of the myristoylated alanine-rich protein kinase C substrate (MARCKS) family of protein kinase C substrates
MacMARCKS has recently been suggested to play a crucial role in regulating the actin cytoskeleton during phagocytosis in macrophages; it is rapidly recruited to the forming phagosome, and expression of a mutant form of the protein lacking an effector domain was reported to completely inhibit phagocytosis in a macrophage cell line [9]
In this report we demonstrate that MacMARCKS associates with phagosomes, its presence is not required for phagocytosis; macrophages derived from MacMARCKS null mice phagocytose zymosan normally
Summary
(Received for publication, August 28, 1998, and in revised form, September 24, 1998). MacMARCKS contains within it a basic effector domain that contains the serine residues that are phosphorylated by protein kinase C, as well as a calcium/calmodulin and actin-binding site. Two previous reports demonstrated that a macrophage cell line expressing a mutant form of MacMARCKS that lacks the effector domain is defective in phagocytosis and cell adhesion MacMARCKS, known as myristoylated alanine-rich protein kinase C substrate (MARCKS)-related protein, is a PKC substrate that binds calcium/calmodulin and actin MacMARCKS has recently been suggested to play a crucial role in regulating the actin cytoskeleton during phagocytosis in macrophages; it is rapidly recruited to the forming phagosome, and expression of a mutant form of the protein lacking an effector domain was reported to completely inhibit phagocytosis in a macrophage cell line [9]. We show that in our hands, the mutant form of MacMARCKS that lacks the effector domain does not associate with phagosomes, does not displace WT MacMARCKS from phagosomes, and does not inhibit phagocytosis when transfected into a macrophage cell line
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