Disease relevance of MARCKS

• The very high frequency of mutations, biallelic mutations and the predicted truncation of protein products suggests that mutations of MARCKS, FLJ11383 and TAF1B are selected, and play a role in the tumorigenesis of MSI-H colorectal carcinomas [1].
• Previously we showed that stimulation of phosphatidylcholine (PtdCho) synthesis by PMA in SK-N-MC human neuroblastoma cells required overexpression of MARCKS, whereas PKCalpha alone was insufficient [2].
• Neuroblastoma and glioma cells differentially express isoforms of protein kinase C (PKC) and myristoylated PKC substrates (e.g. MARCKS) [3].
• Here we compare the expression of MARCKS in human tumor-derived choroidal melanoma cells (OCM-1) and in primary cultures of normal choroidal melanocytes [4].
• No significant stimulation of MARCKS protein phosphorylation was seen in four other insulin-sensitive cell lines, in which insulin is known to activate other protein serine/threonine kinases: HIRC-B, BC3H-1, 3T3-L1 adipocytes, and H35 rat hepatoma cells made to stably express the MARCKS protein [5].

Psychiatry related information on MARCKS

• A number of studies now indicate that lithium has considerable efficacy in the prevention of suicide in patients with affective disorders, and accumulating evidence indicates that protein kinase C (PKC) and its substrates, in particular the myristoylated alanine-rich C kinase substrate (MARCKS), are primary targets of chronic lithium treatment [6].
• Regulation of MARCKS expression may be associated with the prophylactic efficacy of lithium in the long-term stabilization of the recurrent affective episodes in bipolar disorder, and valproate may share this property [7].

High impact information on MARCKS

• The nuclear-localization signal of DGK-zeta is located in a region that is homologous to the phosphorylation-site domain of the MARCKS protein [8].
• We consider here the roles of the major phosphatidylinositol-4,5-diphosphate (PIP2) binding protein, MARCKS, and PIP2 levels in controlling cytoskeleton dynamics [9].
• We conclude by considering the hypothesis that proteins such as MARCKS bind a significant fraction of the PIP2 in a cell, helping to sequester it in lateral membrane domains, then release this lipid in response to local signals such as an increased concentration of Ca(++)/calmodulin or activation of protein kinase C [10].
• We studied the distribution of MARCKS, the alpha isozyme of PKC (PKC alpha), and myosin I in lipopolysaccharide-treated peritoneal macrophages ingesting zymosan particles [11].
• Phagocytosis of zymosan was accompanied by rapid and sustained phosphorylation of MARCKS [11].

Chemical compound and disease context of MARCKS

• Overexpression of MARCKS, but not protein kinase C-alpha, increases phorbol ester-stimulated synthesis of phosphatidylcholine in human SK-N-MC neuroblastoma cells [12].
• Activation of protein kinase C-alpha and translocation of the myristoylated alanine-rich C-kinase substrate correlate with phorbol ester-enhanced noradrenaline release from SH-SY5Y human neuroblastoma cells [13].
• The expression of MARCKS was down-regulated in HCC tissues, as compared with non-tumorous liver cirrhosis tissues from the same patients [14].
• In human neuronal teratoma (NT-2) cells, lysophosphatidic acid (LPA) induced MARCKS phosphorylation dose- and time-dependently [15].

Biological context of MARCKS

• Melanocytes incubated for 48 h with TPA at a higher concentration (100 ng/ml TPA) exhibited suboptimal TPA-stimulated DNA synthesis (28% of maximal) and decreased phosphorylation of the MARCKS substrate protein (50% of maximal) [16].
• Down-regulation of MARCKS expression or disruption of MARCKS function in these cells inhibits the secretory response to subsequent stimulation [17].
• In parallel with the sustained increase in diglyceride formation, CR-mediated phagocytosis was also associated with phosphorylation of a cellular protein kinase C substrate (MARCKS) [18].
• Dephosphorylated cytoplasmic MARCKS would also be free to interact with mucin granule membranes and thus could link granules to the contractile cytoskeleton, mediating their movement to the cell periphery and subsequent exocytosis [17].
• Plasmid constructions containing between 52 and 1453 bp of the human MARCKS promoter linked to the human growth hormone gene were then used in transient expression experiments [19].

Anatomical context of MARCKS

• MARCKS, a major in vivo substrate of protein kinase C, interacts with plasma membranes in a phosphorylation-, myristoylation-, and calmodulin-dependent manner [20].
• The human cDNA was used to demonstrate that tumor necrosis factor-alpha could rapidly stimulate MARCKS gene transcription in the human promyelocytic leukemia cell line HL60 [19].
• Endogenous MARCKS and green fluorescent protein-tagged wild-type MARCKS were translocated from membrane to cytosol upon PMA treatment, further confirming MARCKS activation [21].
• MARCKS protein is a key molecule regulating mucin secretion by human airway epithelial cells in vitro [17].
• These data provide evidence for the identity of the MCE as cathepsin B and suggest that this cleavage most likely takes place within lysosomes, perhaps as a result of specific lysosomal targeting sequences within the MARCKS primary sequence [22].

Associations of MARCKS with chemical compounds

• Myristoylated alanine-rich C kinase substrate (MARCKS) sequesters spin-labeled phosphatidylinositol 4,5-bisphosphate in lipid bilayers [23].
• We previously identified a novel means of regulating cellular MARCKS concentrations that involved a specific proteolytic cleavage of the protein and implicated a cysteine protease in this process (Spizz, G., and Blackshear, P. J. (1996) J. Biol. Chem. 271, 553-562) [22].
• A quantitative analysis obtained with dansyl (5-dimethylaminonaphthalene-1-sulfonyl)-calmodulin showed that myristoylated MARCKS has an affinity higher than the non-myristoylated protein [20].
• The phosphorylation of PKC-delta was inhibited by C3 toxin, demonstrating that the role of MARCKS in NT secretion was regulated by PKC-delta downstream of the Rho/ROK pathway [21].
• The ability of TPA to enhance NA release and to cause the translocation and phosphorylation of MARCKS was inhibited by the PKC inhibitor Ro 31-8220 (10 microM) [13].

Enzymatic interactions of MARCKS

• Furthermore, MARCKS was serine-phosphorylated in liver cirrhosis and HCC, and phosphorylated MARCKS was detected in a cytosolic fraction of these tissues [14].
• Recently, we have demonstrated that MARCKS is phosphorylated at Ser159 in PSD by Rho-kinase in vitro and that the phosphorylation occurred in neuronal cells upon stimulation with lysophosphatidic acid (LPA), and its phosphorylation was inhibited by a novel and specific Rho-kinase inhibitor, H-1152 [24].

Regulatory relationships of MARCKS

• Overexpression of MARCKS enhanced PLD activity 1.3-2.5-fold compared with vector controls in unstimulated cells, and 3-4-fold in cells stimulated with 100 nM PMA [2].
• In keratinocytes, TGF-alpha and EGF induced only a modest increase in MARCKS protein phosphorylation [25].
• In contrast, VEGF stimulated MARCKS phosphorylation without alteration of protein expression during BPMEC proliferation, which may result in reduced interaction between MARCKS and actin or CaM, leading to actin reorganization and MLC phosphorylation [26].
• Thus, in SK-N-MC cells, MARCKS is required for TPA-stimulated synthesis of PtdCho and PKC-alpha alone is insufficient for supporting enhanced synthesis [12].
• Selective PKC inhibitors but not tyrosine kinase inhibitors significantly inhibited the phosphorylation of MARCKS induced by Abeta [27].

Other interactions of MARCKS

• Identification and characterization of cathepsin B as the cellular MARCKS cleaving enzyme [22].
• BBS-mediated NT secretion was attenuated by MARCKS siRNA [21].
• Our results show that MARCKS is an essential link in the PKC-mediated activation of PtdCho-specific PLD in these cells and that the stimulation of PtdCho synthesis by PMA is a secondary response [2].
• Sprouting neuritic components of plaques are immunopositive with other growth-associated proteins, such as GAP43, MARCKS, and spectrin [28].
• Analogous structural motifs in myelin basic protein and in MARCKS [29].

Analytical, diagnostic and therapeutic context of MARCKS

• We expressed human MARCKS mutated in the myristoylation site and the PSD in REF52 cells; the cells were then fractionated by ultracentrifugation [30].
• Titration of the proxyl-PIP(2) EPR signal by the MARCKS-derived peptide also suggests that multiple PI(4,5)P(2) molecules interact with MARCKS [23].
• No differences in quantity or intracellular distribution of PKC activity, PKC isoforms by Western blot analysis, or of the PKC substrate, myristoylated alanine-rich C kinase substrate (MARCKS), were apparent in any of the cells [31].
• After collagenase digestion and Percoll density gradient centrifugation of human renal tissue, tubular epithelial cells of the proximal and the distal segments were isolated with an immunomagnetic method using MACS microbeads [32].
• Molecular cloning and chromosomal mapping of a cDNA encoding human 80K-L protein: major substrate for protein kinase C [33].

References