CLONING AND CHARACTERIZATION OF KIR3.1 (GIRK1) C-TERMINAL ALTERNATIVESPLICE VARIANTS

Southern blot analysis of RT-PCR products from brain and heart reveale d multiple products for a C-terminal region of Kir3.1. Sequencing yiel ded clones for wild-type Kir3.1 and three Kir3.1 C-terminal alternativ e splice variants, including a unique alternative exon. Two of these v ariants encoded truncated Kir3.1 molecules. Tissue distribution and el ectrophysiological characterization of a single truncated variant, Kir 3.1(00) were then examined. Kir3.1 channels are gated by G-protein py- subunits binding to the C-terminal domain, thus, the truncation of Kir 3.1(00) removes a major functional domain. When incorporated into hete romeric channels with other family members (Kir3.1, 3.2 or 3.4) severa l functional changes were observed: (1) Kir3.1(00) changes G-protein a ctivation of Kir3 channels; (2) Kir3.1(00) is restricted in its abilit y to assemble with other channel subunits as heteromers; and (3) incor poration of Kir3.1(00) into heteromeric channel complexes alters the k inetics of channel re-activation.