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E Murrison

Publications and source records attributed to E Murrison.

4 recordsLinked to original sources
PubMed2000

Analysis of the alpha4beta1 integrin-osteopontin interaction.

The integrin alpha4beta1 is involved in mediating exfiltration of leukocytes from the vasculature. It interacts with a number of proteins up-regulated during the inflammatory response including VCAM-1 and the CS-1 alternatively spliced region of fibronectin. In addition it binds the multifunctional protein osteopontin (OPN), which can act as both a cytokine and an extracellular matrix molecule. Here we map the region of human OPN that supports cell adhesion via alpha4beta1 using GST fusion proteins. We show that alpha4beta1 expressed in J6 cells interacts with intact OPN when the integrin is in a high activation state, and by deletion mapping that the alpha4beta1 binding region in OPN lies between amino acid residues 125 and 168 (aa125-168). This region contains the central RGD motif of OPN, which also interacts with integrins alphavbeta3, alphavbeta5, alphavbeta1, alpha8beta1, and alpha5beta1. Mutating the RGD motif to RAD had no effect on the interaction with alpha4beta1. To define the binding site the region incorporating aa125-168 was divided into 5 overlapping peptides expressed as GST fusion proteins. Two peptides supported adhesion via alpha4beta1, aa132-146, and aa153-168; of these only a synthetic peptide, SVVYGLR (aa162-168), derived from aa153-168 was able to inhibit alpha4beta1 binding to CS-1. These data identify the motif SVVYGLR as a novel peptide inhibitor of alpha4beta1, and the primary alpha4beta1 binding site within OPN.

Amino Acid Sequence↗
PubMed2000

A regulated interaction between alpha5beta1 integrin and osteopontin.

The extracellular matrix protein osteopontin (OPN) interacts with a number of integrins, namely alphavbeta1, alphavbeta3, alphavbeta5, alpha9beta1, alpha8beta1, and alpha4beta1. We have investigated the interaction of alpha5beta1 integrin with OPN using K562 cells, which only express alpha5beta1. alpha5beta1 is in a low activation state in this cell line, but can be stimulated to a higher activation state by the phorbol ester TPA. Treating K562 wild-type cells (K562-WT) with TPA stimulated an interaction between alpha5beta1 and OPN. No interaction was seen in the absence of TPA. alpha5beta1 selectively interacted with a GST fusion protein of the N-terminal fragment of OPN (aa17-168), which is generated in vivo by thrombin cleavage of OPN. Expression of the alpha4 integrin in K562 cells (K562-alpha4beta1) stimulated alpha5beta1-dependent binding to aa17-168 in the absence of TPA, suggesting that alpha4beta1 activates alpha5beta1 in K562 cells. Adhesion via alpha5beta1 is mediated by the Arg-Gly-Asp (RGD) motif of OPN, as mutating this sequence to Arg-Ala-Asp (RAD) blocked binding of both cell types. These data demonstrate that thrombin cleavage regulates the adhesive properties of OPN and that alpha5beta1 integrin can interact with thrombin-cleaved osteopontin when in a high activation state.

Amino Acid Sequence↗
PubMed1998

Immunohistochemical localisation of mGluR7 protein in the rodent and human cerebellar cortex using subtype specific antibodies.

Metabotropic glutamate receptors (mGluRs) are a heterogeneous family of G protein coupled receptors that are linked to multiple second messenger systems to regulate neuronal excitability and synaptic transmission. To characterise the protein expression of the two mGluR7 receptor splice variants in human and rat cerebellar cortex, antibodies specific to mGluR7 were generated. Antibodies were raised against a glutathione-S-transferase fusion protein containing amino acid residues located in the extracellular domain common to both the human and rat mGluR7 splice variants. These antibodies specifically detected human mGluR7a in mammalian cells transfected with this receptor. In agreement with mGluR7 in situ hybridisation studies, immunohistochemistry performed at the light microscope level revealed that mGluR7 protein expression occurred most prominently in a particular population of nerve cells common to both the human and rat, located within the cerebellar cortex of gray matter contained within transverse folia. Moreover, strong mGluR7-like immunoreactivity was seen in Purkinje cell body cytoplasm of the Purkinje cell layer. In the most superficial cerebellar cortical layer, the molecular layer, immunostaining was observed in Purkinje cell associated proximal and distal dendritic trees. No detectable labelling was evident in intrinsic deep cerebellar nuclei known to contain GABAergic terminals of projecting Purkinje cell axons. These data are suggestive of a post-synaptic location of mGluR7 in this central nervous system structure. In the rodent, additional non-Purkinje cells thought to represent inhibitory interneurones were labelled at all levels in the molecular layer. mGluR7-like immunoreactivity was not associated with glial cells.

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