Biomedical subjects

Adrienne Frostholm

Publications and source records attributed to Adrienne Frostholm.

3 recordsLinked to original sources

PubMed2006

Intracellular substrates of brain-enriched receptor protein tyrosine phosphatase rho (RPTPrho/PTPRT).

Receptor protein tyrosine phosphatase rho (RPTPrho/PTPRT) is a transmembrane protein that is highly expressed in the developing and adult central nervous system. It is a member of the RPTP R2B subfamily, which includes PTPkappa, PTPmu and PCP-2. Glutathione-S-transferase (GST) pulldown assays were used to show that RPTPrho interacts with several adherens junctional proteins in brain, including E-cadherin, N-cadherin, VE-cadherin (cadherin-5), desmoglein, alpha, beta and gamma catenin, p120(ctn) and alpha-actinin. With the exception of E-cadherin and alpha-actinin, binding was considerably reduced at high sodium concentrations. Furthermore, immunoprecipitation phosphatase assays indicated that E-cadherin, and to a far lesser extent p120(ctn), were tyrosine dephosphorylated by a recombinant RPTPrho intracellular fragment, and thus, were likely to be primary substrates for RPTPrho. The interaction of RPTPrho with adherens junctional components suggests that this phosphatase may transduce extracellular signals to the actin cytoskeleton and thereby play a role in regulating cadherin-mediated cell adhesion in the central nervous system.

Adherens Junctions↗

PubMed2004

Genomic structure and alternative splicing of murine R2B receptor protein tyrosine phosphatases (PTPkappa, mu, rho and PCP-2).

BACKGROUND: Four genes designated as PTPRK (PTPkappa), PTPRL/U (PCP-2), PTPRM (PTPmu) and PTPRT (PTPrho) code for a subfamily (type R2B) of receptor protein tyrosine phosphatases (RPTPs) uniquely characterized by the presence of an N-terminal MAM domain. These transmembrane molecules have been implicated in homophilic cell adhesion. In the human, the PTPRK gene is located on chromosome 6, PTPRL/U on 1, PTPRM on 18 and PTPRT on 20. In the mouse, the four genes ptprk, ptprl, ptprm and ptprt are located in syntenic regions of chromosomes 10, 4, 17 and 2, respectively. RESULTS: The genomic organization of murine R2B RPTP genes is described. The four genes varied greatly in size ranging from approximately 64 kb to approximately 1 Mb, primarily due to proportional differences in intron lengths. Although there were also minor variations in exon length, the number of exons and the phases of exon/intron junctions were highly conserved. In situ hybridization with digoxigenin-labeled cRNA probes was used to localize each of the four R2B transcripts to specific cell types within the murine central nervous system. Phylogenetic analysis of complete sequences indicated that PTPrho and PTPmu were most closely related, followed by PTPkappa. The most distant family member was PCP-2. Alignment of RPTP polypeptide sequences predicted putative alternatively spliced exons. PCR experiments revealed that five of these exons were alternatively spliced, and that each of the four phosphatases incorporated them differently. The greatest variability in genomic organization and the majority of alternatively spliced exons were observed in the juxtamembrane domain, a region critical for the regulation of signal transduction. CONCLUSIONS: Comparison of the four R2B RPTP genes revealed virtually identical principles of genomic organization, despite great disparities in gene size due to variations in intron length. Although subtle differences in exon length were also observed, it is likely that functional differences among these genes arise from the specific combinations of exons generated by alternative splicing.

Alternative Splicing↗

PubMed2004

Digital transcriptome analysis in the aging cerebellum.

Serial analysis of gene expression (SAGE) was used to identify and quantify all expressed cerebellar genes in the adult (P92) and aged (P810) C57BL/6J mouse cerebellum. A "closest-neighbor" algorithm was used to differentiate low abundance tags from possible sequencing errors in both libraries. Unique tags were categorized into four groups: (1) novel genes; (2) ESTs; (3) RIKEN, KIA, and hypothetical genes; and (4) known genes. Known genes were further subdivided into functional categories based on the gene ontology classification, using a web-based program developed in this laboratory (MmSAGEClass). Comparison of adult and aged cerebellar libraries revealed several genes that were differentially expressed, including growth hormone and prolactin, both of which were markedly decreased in the aged cerebellum. In addition, several tags showing differential expression were not identified in the Unigene database and are likely to represent novel genes. The present SAGE data on the aged cerebellar transcriptome may reveal candidate genes involved in the aging process.

Aging↗