[MAGUKs: beyond ionic channel anchoring].

A family of anchoring proteins named MAGUK (for membrane associated guanylate kinase) has emerged as a key element in the organization of protein complexes in specialized membrane regions. These proteins are characterized by the presence of multipe protein-protein interaction domains including PDZ and SH3 domains. The MAGUK family comprises the post-synaptic density 95 (PSD-95) protein and closely related molecules such as chapsyn-110, synapse-associated protein 102 (SAP-102), and SAP-97.

Different isoforms of synapse-associated protein, SAP97, are expressed in the heart and have distinct effects on the voltage-gated K+ channel Kv1.5.

The SAP97 isoforms differ by alternatively spliced insertion domains that regulate protein localization and oligomerization. We used reverse transcription-PCR to identify SAP97 isoforms of human and rat myocardium. In Chinese hamster ovary cells, cloned protein expression was studied using Western blot, confocal imaging of green fluorescent protein-tagged proteins, and patch clamp technique.

Expression, regulation and role of the MAGUK protein SAP-97 in human atrial myocardium.

Objective: In various cell types, membrane-associated guanylate kinases proteins called MAGUK play a major role in the spatial localization and clustering of ion channels. Here, we studied the expression and role of these anchoring proteins in human right atrial myocardium by means of various molecular, biochemical and physiological methods.

Methods And Results: SAP-97, PSD-95, Chapsyn and SAP-102 messengers were detected by reverse transcriptase-polymerase chain reaction (RT-PCR) on mRNA extracted from both whole myocardium and isolated myocytes.

Dedifferentiation of atrial myocytes during atrial fibrillation: role of fibroblast proliferation in vitro.

Objectives: Severe myocyte alterations, characterized by enlarged myocytes and myolysis, is observed in fibrillating and dilated atria and contributes to atrial fibrillation. The aim of this study was to determine the nature of this cellular remodeling process and factors involved in its regulation.

Methods: In vivo, contractile proteins were studied in 24 human right atrial specimens by means of immunohistochemical techniques.

Mechanisms of action of antiarrhythmic agent bertosamil on hKv1.5 channels and outward potassium current in human atrial myocytes.

We analyzed the mechanism of action of the antiarrhythmic agent bertosamil on hKv1.5 channels expressed in Chinese hamster ovary cells (I(hKv1.5)) and on the outward current (I(o)) of human atrial myocytes (HAMs) by using the whole cell patch-clamp technique to record current.