Melanocortin 4 receptor signals at the neuronal primary cilium to control food intake and body weight.

The melanocortin 4 receptor (MC4R) plays a critical role in the long-term regulation of energy homeostasis, and mutations in the MC4R are the most common cause of monogenic obesity. However, the precise molecular and cellular mechanisms underlying the maintenance of energy balance within MC4R-expressing neurons are unknown. We recently reported that the MC4R localizes to the primary cilium, a cellular organelle that allows for partitioning of incoming cellular signals, raising the question of whether the MC4R functions in this organelle.

Functional characterization and molecular cloning of the K+-dependent Na+/Ca2+ exchanger in intact retinal cone photoreceptors.

Light-dependent changes in cytoplasmic free Ca(2+) are much faster in the outer segment of cone than rod photoreceptors in the vertebrate retina. In the limit, this rate is determined by the activity of an electrogenic Na(+)/Ca(2+) exchanger located in the outer segment plasma membrane. We investigate the functional properties of the exchanger activity in intact, single cone photoreceptors isolated from striped bass retina.

Cloning and molecular characterization of cGMP-gated ion channels from rod and cone photoreceptors of striped bass ( M. saxatilis ) retina.

Vertebrate photoreceptors respond to light with changes in membrane conductance that reflect the activity of cyclic-nucleotide gated channels (CNG channels). The functional features of these channels differ in rods and cones; to understand the basis of these differences we cloned CNG channels from the retina of striped bass, a fish from which photoreceptors can be isolated and studied electrophysiologically. Through a combination of experimental approaches, we recovered and sequenced three full-length cDNA clones.

Endocytosis and vesicle recycling at a ribbon synapse.

At ribbon synapses, where exocytosis is regulated by graded depolarization, vesicles can fuse very rapidly with the plasma membrane (complete discharge of the releasable pool in approximately 200 msec). Vesicles are also retrieved very rapidly (time constant of approximately 1 sec), leading us to wonder whether their retrieval uses an unusual mechanism. To study this, we exposed isolated bipolar neurons from goldfish retina to cationized ferritin.