Membrane Targeting by C1 and C2 Domains

Abstract

protein kinase C phospholipase A2 cytosolic phospholipase A2 gastrin-releasing peptide fragment green fluorescent protein diacylglycerol phosphatidylcholine phosphatidylserine phorbol 12-myristate 13-acetate Many peripheral proteins involved in cell signaling translocate to different cell membranes in response to specific cell stimuli. Because cellular functions and regulation of these proteins depend on their specific subcellular localization (1Teruel M.N. Meyer T. Cell. 2000; 103: 181-184Abstract Full Text Full Text PDF PubMed Scopus (192) Google Scholar), understanding the mechanisms of membrane targeting is of great importance. The membrane targeting of diverse peripheral proteins is mediated by a limited number of membrane-targeting domains, including protein kinase C (PKC)1conserved 1 (C1), PKC conserved2 (C2), and pleckstrin homology domains. Recent structural and functional studies of individual membrane targeting domains as well as the peripheral proteins harboring these domains have provided new insights into the molecular mechanisms underlying the specific subcellular targeting and activation of peripheral proteins. This review summarizes the recent progress in our understanding of the mechanisms of C1 and C2 domain-mediated membrane targeting, with an emphasis on the correlation between the membrane binding properties of the C1 and C2 domains and the peripheral proteins containing these domains and their subcellular targeting behaviors. There are several excellent reviews (2Nalefski E.A. Falke J.J. Protein Sci. 1996; 5: 2375-2390Crossref PubMed Scopus (687) Google Scholar, 3Rizo J. Sudhof T.C. J. Biol. Chem. 1998; 273: 15879-15882Abstract Full Text Full Text PDF PubMed Scopus (705) Google Scholar, 4Ron D. Kazanietz M.G. FASEB J. 1999; 13: 1658-1676Crossref PubMed Scopus (552) Google Scholar, 5Rebecchi M.J. Scarlata S. Annu. Rev. Biophys. Biomol. Struct. 1998; 27: 503-528Crossref PubMed Scopus (249) Google Scholar, 6Hurley J.H. Misra S. Annu. Rev. Biophys. Biomol. Struct. 2000; 29: 49-79Crossref PubMed Scopus (225) Google Scholar) that contain more exhaustive surveys on the membrane targeting domains. The membrane binding of peripheral proteins involves different types of interactions (Fig. 1) that depend upon the physicochemical properties of both membrane and protein. Membranes of different cellular compartments have different compositions of bulk lipids that can modulate membrane targeting of proteins either by providing unique microenvironments or by producing specific lipid metabolites, such as diacylglycerol (DAG) and phosphoinositides, that function as second messengers. Extensive structural and mutational studies of phospholipases A2(PLA2) have shown that their membrane binding surfaces are composed of cationic, aliphatic, and aromatic residues (7Gelb M.H. Cho W. Wilton D.C. Curr. Opin. Struct. Biol. 1999; 9: 428-432Crossref PubMed Scopus (116) Google Scholar). A recent study by surface plasmon resonance analysis indicated that cationic residues primarily accelerate the association of protein to anionic membrane surfaces, whereas aliphatic residues mainly slow the membrane dissociation by penetrating into the hydrophobic core of the membrane (8Stahelin R.V. Cho W. Biochemistry. 2001; 40: 4672-4678Crossref PubMed Scopus (145) Google Scholar). Aromatic residues, particularly Trp, which has a preference for the water-lipid interface (9Yau W.M. Wimley W.C. Gawrisch K. White S.H. Biochemistry. 1998; 37: 14713-14718Crossref PubMed Scopus (824) Google Scholar), play a pivotal role in binding to zwitterionic PC membranes (7Gelb M.H. Cho W. Wilton D.C. Curr. Opin. Struct. Biol. 1999; 9: 428-432Crossref PubMed Scopus (116) Google Scholar, 10Han S.K. Kim K.P. Koduri R. Bittova L. Munoz N.M. Leff A.R. Wilton D.C. Gelb M.H. Cho W. J. Biol. Chem. 1999; 274: 11881-11888Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar) by affecting both membrane association and dissociation steps (8Stahelin R.V. Cho W. Biochemistry. 2001; 40: 4672-4678Crossref PubMed Scopus (145) Google Scholar). A priori, the physicochemical principles learned from these in vitromembrane binding studies should allow the prediction of the subcellular targeting behaviors of peripheral proteins, provided that the subcellular targeting is driven mainly by membrane-protein interactions. The C1 domain (∼50 amino acids) is a cysteine-rich compact structure that contains five short β strands, a short α-helix, and two zinc ions (Fig. 2) (11Hommel U. Zurini M. Luyten M. Struct. Biol. 1994; 1: 383-387Crossref PubMed Scopus (137) Google Scholar, 12Zhang G. Kazanietz M.G. Blumberg P.M. Hurley J.H. Cell. 1995; 81: 917-924Abstract Full Text PDF PubMed Scopus (595) Google Scholar). The C1 domain was first identified as the interaction site for DAG and phorbol ester in PKCs (13Nishizuka Y. Nature. 1988; 334: 661-665Crossref PubMed Scopus (3532) Google Scholar). In conventional (α, βI, βII, and γ) and novel (δ, ε, θ, and η) PKCs, the C