期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 277, 期 33, 页码 30183-30190出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M203072200
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资金
- NIDDK NIH HHS [5F32DK09912-02, 2P50DK39255, DK57683-01] Funding Source: Medline
In an attempt to find podocyte-expressed proteins that may interact with the tight junction protein MAGI-1, we screened a glomerulus-enriched cDNA library with a probe consisting of both WW domains of MAGI-1. One of the isolated clones contained two WW domain-binding motifs and was identified as a portion of the actin-bundling protein synaptopodin. In vitro binding assays confirmed this interaction between MAGI-1 and synaptopodin and identified the second WW domain of MAGI-1 to be responsible for the interaction. MAGI-1 and synaptopodin can also interact in vivo, as they can be immunoprecipitated together from HEK293 cell lysates. Another actin-bundling protein that is found in glomerular podocytes and shown to be mutated in an inheritable form of glomerulosclerosis is alpha-actinin-4. We show that a-actinin-4 is also capable of binding to MAGI-1 in in vitro binding assays and that this interaction is mediated by the fifth PDZ domain of MAGI-1 binding to the C terminus of alpha-actinin-4. Exogenously expressed synaptopodin and alpha-actinin-4 were found to colocalize along with endogenous MAGI-1 at the tight junction of Madin-Darby canine kidney cells. The interaction and colocalization of MAGI-1 with two actin-bundling proteins suggest that MAGI-1 may play a role in actin cytoskeleton dynamics within polarized epithelial cells.
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