Article

Phosphorylation of NG2 proteoglycan by protein kinase C-alpha regulates polarized membrane distribution and cell motility.

Cancer Research Center, The Burnham Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA.
Journal of Biological Chemistry (Impact Factor: 4.6). 01/2005; 279(53):55262-70. DOI: 10.1074/jbc.M411045200
Source: PubMed

ABSTRACT Protein kinase C (PKC)-alpha phosphorylation of recombinant NG2 cytoplasmic domain and phorbol ester-induced PKC-dependent phosphorylation of full-length NG2 expressed in U251 cells are both blocked by mutation of Thr(2256), identifying this residue as a primary phosphorylation site. In untreated U251/NG2 cells, NG2 is present along with ezrin and alpha(3)beta(1) integrin in apical cell surface protrusions. Phorbol ester treatment causes redistribution of all three components to lamellipodia, accompanied by increased cell motility. U251 cells expressing NG2 with a valine substitution at position 2256 are resistant to phorbol ester treatment: NG2 remains in membrane protrusions and cell motility is unchanged. In contrast, NG2 with a glutamic acid substitution at position 2256 redistributes to lamellipodia even without phorbol ester treatment, rendering transfected U251 cells spontaneously motile. PKC-alpha-mediated NG2 phosphorylation at Thr(2256) is therefore a key step for initiating cell polarization and motility.

0 Bookmarks
 · 
46 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Chondroitin sulfate proteoglycan 4 (CSPG4), a transmembrane proteoglycan originally identified in melanoma cells, has been reported to be expressed in breast cancer cells. This study was performed to examine the expression and significance of CSPG4 in a cohort of breast cancer patients. Immunohistochemical analysis of CSPG4 was performed on tissue microarrays constructed from tissue specimens from 240 breast cancer patients. CSPG4 staining was correlated with clinical and pathological characteristics, overall survival (OS), and disease recurrence. Contradicting to a previous report, our results showed that high CSPG4 expression was not related to triple-negative status of breast cancer patients. The Kaplan-Meier method showed that high CSPG4 expression was significantly associated with shorter time to recurrence (TTR). Patients with high CSPG4 expression had poorer OS and shorter TTR in a multivariate survival analysis after adjustment for stage, tumor grade, expression of estrogen receptor and progesterone receptor, and HER2 overexpression. This study showed that high CSPG4 expression correlates with disease recurrence and OS in breast cancers.
    Biochemical and Biophysical Research Communications 10/2013; · 2.28 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Brain inflammation plays a key role in neurological disease. Although much research has been conducted investigating inflammatory events in animal models, potential differences in human brain versus rodent models makes it imperative that we also study these phenomena in human cells and tissue.
    Journal of Neuroinflammation 06/2014; 11(1):104. · 4.90 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The role of glia in modulating neuronal network activity is an important question. Oligodendrocyte precursor cells (OPC) characteristically express the transmembrane proteoglycan nerve-glia antigen 2 (NG2) and are unique glial cells receiving synaptic input from neurons. The development of NG2+ OPC into myelinating oligodendrocytes has been well studied, yet the retention of a large population of synapse-bearing OPC in the adult brain poses the question as to additional functional roles of OPC in the neuronal network. Here we report that activity-dependent processing of NG2 by OPC-expressed secretases functionally regulates the neuronal network. NG2 cleavage by the α-secretase ADAM10 yields an ectodomain present in the extracellular matrix and a C-terminal fragment that is subsequently further processed by the γ-secretase to release an intracellular domain. ADAM10-dependent NG2 ectodomain cleavage and release (shedding) in acute brain slices or isolated OPC is increased by distinct activity-increasing stimuli. Lack of NG2 expression in OPC (NG2-knockout mice), or pharmacological inhibition of NG2 ectodomain shedding in wild-type OPC, results in a striking reduction of N-methyl-D-aspartate (NMDA) receptor-dependent long-term potentiation (LTP) in pyramidal neurons of the somatosensory cortex and alterations in the subunit composition of their α-amino-3-hydroxy-5-methyl-4-isoxazolepr opionicacid (AMPA) receptors. In NG2-knockout mice these neurons exhibit diminished AMPA and NMDA receptor-dependent current amplitudes; strikingly AMPA receptor currents can be rescued by application of conserved LNS protein domains of the NG2 ectodomain. Furthermore, NG2-knockout mice exhibit altered behavior in tests measuring sensorimotor function. These results demonstrate for the first time a bidirectional cross-talk between OPC and the surrounding neuronal network and demonstrate a novel physiological role for OPC in regulating information processing at neuronal synapses.
    PLoS Biology 11/2014; 12(11):e1001993. · 11.77 Impact Factor