ABSTRACT
KCNE1-5 are type I membrane proteins with a single TM domain anked by extracellular N-and intracellular C-termini. ey are tiny proteins (100-180 aa), contain multiple N-glycosylation sites 28, 29, and share modest sequence similarity in their TM domain and C-terminus that is predicted to be juxtaposed to the inner leaet of the membrane. KCNE proteins are essentially found throughout the human body. KCNE1 is expressed in heart (Barhanin et al. 1996), brain (Ohya et al. 2002), lung (Grahammer et al. 2001b), kidney (Barriere et al. 2003), testis (Tsevi et al. 2005), small intestine (Dedek and Waldegger 2001), exocrine pancreas (evenod 2002), inner ear (Vetter et al. 1996), and peripheral blood leukocytes (Chouabe et al. 1997). According to Lundquist, there are two KCNE1 splice variants: KCNE1a, which is expressed more ubiquitously, and KCNE1b, which is predominantly found in heart (Lundquist et al. 2006). KCNE2 is widely expressed in brain (Tinel et al. 2000), eye (Warth and Barhanin 2002), heart (Tinel et al. 2000), skeletal muscle (Abbott et al. 1999), stomach (Grahammer et al. 2001b), lung (Warth and Barhanin 2002), heart (Tinel et al. 2000a), bladder, and kidney (Ohya et al. 2002). A small but signicant expression of KCNE2 was found in liver, ovary, testis, prostate, small intestine, and leukocytes. KCNE3 is highly expressed in kidney (Warth and Barhanin 2002), skeletal muscle (Abbott et al. 2001a), brain (Abbott et al. 2001a), and heart (Abbott et al. 2001a), with moderate levels in small intestine (Dedek and Waldegger 2001). KCNE4 is predominantly expressed in reproductive system (embryo and adult uterus), with low expression found in kidney, small intestine, lung, and heart (Grunnet et al. 2002). e last family member, KCNE5, is expressed in heart, skeletal muscle, brain, spinal cord, and placenta (Piccini et al. 1999). In sum, at least at mRNA level, KCNEs are ubiquitously expressed.
