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The main inhibitory neurotransmitter receptors in the adult central nervous system (CNS) are type A γ-aminobutyric acid receptors (GABAARs) and glycine receptors (GlyRs). Synaptic responses mediated by GlyR and GABAAR display a hyperpolarizing shift during development. This shift relies mainly on the developmental up-regulation of the K+-Cl− co-transporter KCC2 responsible for the extrusion of Cl−. In mature neurons, altered KCC2 function—mainly through increased endocytosis—leads to the re-emergence of depolarizing GABAergic and glycinergic signaling, which promotes hyperexcitability and pathological activities. Identifying signaling pathways and molecular partners that control KCC2 surface stability thus represents a key step in the development of novel therapeutic strategies. Here, we present our current knowledge on the cellular and molecular mechanisms governing the plasma membrane turnover rate of the transporter under resting conditions and in response to synaptic activity. We also discuss the notion that KCC2 lateral diffusion is one of the first parameters modulating the transporter membrane stability, allowing for rapid adaptation of Cl− transport to changes in neuronal activity. [ABSTRACT FROM AUTHOR]

Many crabs possess fused rhabdoms which are partly broken down at dawn and re-synthesised at dusk. The cross-sectional area of the rhabdom is therefore smaller during the day than at night. The only previously described mechanism of membrane removal from the rhabdomere in Crustacea involves the formation of pinocytotic vesicles at the bases of the microvilli. The geometry of the rhabdom is such that uniform pinocytosis across the base of each rhabdomere would result in a stack of orthogonally oriented rectangles. In the process described here, microvilli from the outer edges of the rhabdomeres are engulfed by adjacent retinula cells, reducing the number as well as the length of the microvilli and maintaining the smooth longitudinal profile needed for optimal functioning of the rhabdom. [ABSTRACT FROM AUTHOR]

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Capacitance changes in cell-attached patches of rat melanotrophs were measured by a high-frequency lock-in amplifier. The background noise of around 30 aF allowed the detection of discrete steps due to fission (endocytosis) and fusion (exocytosis) of vesicles with diameters as small as 60 nm. The amplitude of both types of steps was similar with a modal value of around 300 aF. The frequency of these steps was not changed, if secretagougues such as ionomycin and/or dibutyril cAMP, were applied to the bathing solution. Moreover, this treatment did not result in an increased appearance of expected 2000 to 3000 aF steps due to exocytosis of secretory granules. We conclude that the likely explanation for recorded capacitance steps is that they represent the constitutive vesicle traffic. From the typical frequency and amplitude of these events (around 1 min–1, 300 aF) in a membrane patch (26 fF) it is estimated that the whole membrane of a rat melanotroph may be ingested under our conditions in 1 to 2 h. [ABSTRACT FROM AUTHOR]