Mat-8, a novel phospholemman-like protein expressed in human breast tumors, induces a chloride conductance in Xenopus oocytes

Briggs W. Morrison, J. Randall Moorman, Gopal C. Kowdley, Yvonne M. Kobayashi, Larry R. Jones, Philip Leder

Research output: Contribution to journalArticle

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We recently identified a novel 8-kDa transmembrane protein, Mat-8, that is expressed in a subset of murine breast tumors. We have now cloned a cDNA encoding the human version of Mat-8 and show that it is expressed both in primary human breast tumors and in human breast tumor cell lines. The extracellular and transmembrane domains of Mat-8 are homologous to those of phospholemman (PLM), the major plasmalemmal substrate for cAMP-dependent protein kinase and protein kinase C in several different tissues. PLM, which induces chloride currents when expressed in Xenopus oocytes, contains consensus phosphorylation sites for both cAMP-dependent protein kinase A and protein kinase C in its cytoplasmic domain. In contrast, the cytoplasmic domain of Mat-8 contains no such consensus phosphorylation sites and is, in fact, unrelated to the cytoplasmic domain of PLM. RNA blot analysis reveals that Mat-8 and PLM exhibit distinct tissue-specific patterns of expression. We show that expression of Mat-8 in Xenopus oocytes induces hyperpolarization-activated chloride currents similar to those induced by PLM expression. These findings suggest that Mat-8 and PLM, the products of distinct genes, are related proteins that serve as Cl- channels or Cl- channel regulators but have different roles in cell and organ physiology.

Original languageEnglish (US)
Pages (from-to)2176-2182
Number of pages7
JournalJournal of Biological Chemistry
Issue number5
StatePublished - Feb 3 1995


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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