rbr1@columbia.edu

PROFESSOR OF PHARMACOLOGY

Regulation of cardiac ion channels and autonomic signal transduction cascades by development and disease, and over-expression of these channels in cardiac cells or in stem cells coupled to cardiac cells for treatment of cardiac disease.

We are concerned with elucidating the processes that control developmental regulation of cardiac ion channel expression (i.e. electrical behavior) and cardiac autonomic responsiveness (i.e. sensitivity to neurotransmitters), and using that knowledge to design gene- and cell-based therapies for cardiac disease.

We use isolated single heart cells, heart cells grown in culture, and heart cells grown together in culture with neurons or mesenchymal stem cells. To study these preparations we employ a range of techniques, including standard electrophysiology, whole cell voltage clamp and fluorescence microscopy with ion sensitive dyes. By studying both native cardiac channels and recombinant channels over-expressed in myocytes we explore the molecular mechanisms that control channel function within the heart cell and the impact of development and disease on these mechanisms. We also take advantage of transgenic animals in which selected signaling elements have been disrupted or altered.

We have identified age-dependent differences in the function and expression of several cardiac ionic channels (including I_Na, I_Ca,L and I_f), and also differences in autonomic signal transduction cascades (including a- and b-adrenergic and cholinergic) that modulate these and other ionic channels in the heart. We have further found that neurons exert a trophic influence to modify heart cell development that can account for some of the age-dependent effects on ion channel function and the cardiac cell's response to autonomic agonists. Both neurally released peptides (e.g., NPY) and more familiar neurotransmitters (e.g., norepinephrine) can serve as developmental factors. Our increasing understanding of the factors that regulate channel function within the heart cell allows us to develop genetic therapies in which selected channels are over-expressed in the in situ heart, either within the myocytes or in stem cells that then couple to the myocytes, for the purpose of regulating cardiac rhythm.

Selected Publications:

1. Qu J, Plotnikov AN, Danilo P Jr, Shlapakova I, Cohen IS, Robinson RB and Rosen MR: Expression and function of a biological pacemaker in canine heart. Circulation 107:1106-1109, 2003. Abstract PDF File

2. Protas L, Barbuti A, Qu J, Rybin VO, Palmiter RD, Steinberg SF and Robinson RB: Neuropeptide Y is an essential in vivo developmental regulator of cardiac I_Ca,L. Circ. Res. 93:972-979, 2003. Abstract PDF File

3. Plotnikov AN, Sosunov EA, Qu J, Shlapakova IN, Anyukhovsky EP, Liu L, Janse MJ, Brink PR, Cohen IS, Robinson RB, Danilo P Jr and Rosen MR: Biological pacemaker implanted in canine left bundle branch provides ventricular escape rhythms that have physiologically acceptable rates. Circulation 109:506-512, 2004. Abstract PDF File

4. Potapova I, Plotnikov A, Lu Z, Danilo P Jr, Valiunas V, Qu J, Doronin S, Zuckerman J, Shlapakova IN, Gao J, Pan Z, Herron AJ, Robinson RB, Brink PR, Rosen MR and Cohen IS: Human mesenchymal stem cells as a gene delivery system to create cardiac pacemakers. Circ. Res. 94:952-959, 2004. Abstract PDF File

5. Besana A, Barbuti A, Tateyama MA, Symes AJ, Robinson RB and Feinmark SJ: Activation of PKCe inhibits the two-pore domain K⁺ channel, TASK-1, inducing repolarization abnormalities in cardiac ventricular myocytes. J. Biol. Chem. 279:33154-33160, 2004. Abstract PDF File

6. Qu J, Kryukova Y, Potapova IA, Doronin SV, Larsen M, Krishnamurthy G, Cohen IS and Robinson RB: MiRP1 modulates HCN2 channel expression and gating in cardiac myocytes. J. Biol. Chem. 279:43497-43502, 2004. Abstract PDF File

7. Valiunas V, Polosina YY, Miller H, Potapova IA, Valiuniene L, Doronin S, Mathias RT, Robinson RB, Rosen MR, Cohen IS and Brink PR. Connexin-specific cell-to-cell transfer of short interfering RNA by gap junctions. J. Physiol. (Lond) 568:459-468, 2005. Abstract PDF File

Heart rate is controlled by ion currents that flow through protein pores (or channels) spanning the cell membrane. One channel that contributes to heart rate is called HCN (Hyperpolarization-activated, Cyclic Nucleotide-gated), and the current that flows through this channel is known as the pacemaker current. To explore the contribution of HCN channels to cardiac rhythm, we expressed the HCN2 isoform in heart cells taken from newborn rat ventricle and grown in culture. These cells have a small native pacemaker current (top left: current recordings) and spontaneously beat slowly (top right: action potential recordings). Expression of HCN2 markedly increases the pacemaker current (lower left). In addition, heart cells that express HCN2 beat much faster than normal and have a more pronounced slow depolarization between beats (lower right).