G protein-gated inhibitory module of N-type (ca(v)2.2) ca2+ channels.

Voltage-dependent G protein (Gbetagamma) inhibition of N-type (CaV2.2) channels supports presynaptic inhibition and represents a central paradigm of channel modulation. Still controversial are the proposed determinants for such modulation, which reside on the principal alpha1B channel subunit. These include the interdomain I-II loop (I-II), the carboxy tail (CT), and the amino terminus (NT). Here, we probed these determinants and related mechanisms, utilizing compound-state analysis with yeast two-hybrid and mammalian cell FRET assays of binding among channel segments and G proteins. Chimeric channels confirmed the unique importance of NT. Binding assays revealed selective interaction between NT and I-II elements. Coexpressing NT peptide with Gbetagamma induced constitutive channel inhibition, suggesting that the NT domain constitutes a G protein-gated inhibitory module. Such inhibition was limited to NT regions interacting with I-II, and G-protein inhibition was abolished within alpha1B channels lacking these NT regions. Thus, an NT module, acting via interactions with the I-II loop, appears fundamental to such modulation.

Children and Adults With Rare Diseases Need Innovative Medical Devices.

Rare diseases (RD) affect approximately 30 million Americans, half of whom are children. This study is the first to comprehensively evaluate their medical device needs via a survey of physicians. The study sought to identify and document the presumed unmet diagnostic and therapeutic device needs for RD management; clarify the magnitude of the potential unmet need; and generate meaningful data to inform medical device stakeholders. A cross-sectional nonprobability survey was conducted. The study population was drawn from the membership files of four groups: FDA Medical Devices Advisory Committee, Pediatric Advisory Committee, Pediatric Device Consortia, and National Institutes of Health (NIH) Rare Diseases Clinical Research Network. Only physician respondents with experience or knowledge regarding RD were eligible. Among eligible respondents, 90% confirmed the need for innovative devices to care for people with RD. Over 850 device needs were identified for 436 RD, with 74% of needs related to children. Pediatric physicians (OR = 2.11, 95% CI 1.01-4.39, P = 0.046) and physicians with more RD experience reflected greater dissatisfaction with existing devices (OR = 4.49, 95% CI 2.25-8.96, P < 0.0001). Creation of entirely new devices is the top recommendation for mitigating needs. This study demonstrates a major public health need for innovative medical devices to care for children and adults with RD. FDA and NIH support and seek opportunities to accelerate device development for these vulnerable patients.

Custom distinctions in the interaction of G-protein beta subunits with N-type (CaV2.2) versus P/Q-type (CaV2.1) calcium channels.

Inhibition of N- (Cav2.2) and P/Q-type (Cav2.1) calcium channels by G-proteins contribute importantly to presynaptic inhibition as well as to the effects of opiates and cannabinoids. Accordingly, elucidating the molecular mechanisms underlying G-protein inhibition of voltage-gated calcium channels has been a major research focus. So far, inhibition is thought to result from the interaction of multiple proposed sites with the Gbetagamma complex (Gbetagamma). Far less is known about the important interaction sites on Gbetagamma itself. Here, we developed a novel electrophysiological paradigm, "compound-state willing-reluctant analysis," to describe Gbetagamma interaction with N- and P/Q-type channels, and to provide a sensitive and efficient screen for changes in modulatory behavior over a broad range of potentials. The analysis confirmed that the apparent (un)binding kinetics of Gbetagamma with N-type are twofold slower than with P/Q-type at the voltage extremes, and emphasized that the kinetic discrepancy increases up to ten-fold in the mid-voltage range. To further investigate apparent differences in modulatory behavior, we screened both channels for the effects of single point alanine mutations within four regions of Gbeta1, at residues known to interact with Galpha. These residues might thereby be expected to interact with channel effectors. Of eight mutations studied, six affected G-protein modulation of both N- and P/Q-type channels to varying degrees, and one had no appreciable effect on either channel. The remaining mutation was remarkable for selective attenuation of effects on P/Q-, but not N-type channels. Surprisingly, this mutation decreased the (un)binding rates without affecting its overall affinity. The latter mutation suggests that the binding surface on Gbetagamma for N- and P/Q-type channels are different. Also, the manner in which this last mutation affected P/Q-type channels suggests that some residues may be important for "steering" or guiding the protein into the binding pocket, whereas others are important for simply binding to the channel.