Calcium influx through ‘L’‐type channels into rat anterior pituitary cells can be modulated in two ways by protein kinase C (PKC‐isoform selectivity of 1,2‐dioctanoyl sn‐glycerol?)

Abstract

The depolarisation‐induced influx of 45Ca2+ into anterior pituitary tissue and GH3 cells through ‘L’‐type, nimodipine‐sensitive channels was investigated. In anterior pituitary prisms, phorbol esters, activators of protein kinase C, caused an enhancement of K+‐induced 45Ca2+ influx. However, in the GH3 anterior pituitary cell line, phorbol esters inhibited K+‐induced 45Ca2+ influx. The modulation by phorbol esters in both tissues was stereo‐specific and time‐ and concentration‐dependent. The diacylglycerol analogue, 1,2‐dioctanoyl sn‐glycerol was able to mimic the phorbol ester‐induced enhancement of calcium influx into anterior pituitary pieces, but was ineffective in GH3 cell. 1,2‐Diactanoyl sn‐glycerol may selectively activate an isoform of protein kinase C which is responsible for enhanced ‘L’‐type Ca2+‐channel activity.

CCL5 evokes calcium signals in microglia through a kinase‐, phosphoinositide‐, and nucleotide‐dependent mechanism

“…In this series of experiments, we sought to determine whether kinase activation was required for the CCL5‐induced [Ca 2+ ] i increase in microglia. Protein kinase C (PKC) can modulate a variety of Ca 2+ channels, including L‐type voltage‐operated calcium channels (MacEwan and Mitchell,1991), so we determined the role of this kinase in the CCL5 response. Treatment of microglia with 2 μM Ro 31‐8220, a concentration that we have shown to inhibit PKC under similar recording conditions (Usachev et al,2002), did not affect the CCL5‐evoked response, suggesting that PKC activation is not required for an increase in [Ca 2+ ] i (Fig.…”

Protein-tyrosine Kinases Activate while Protein-tyrosine Phosphatases Inhibit L-type Calcium Channel Activity in Pituitary GH3 Cells

“…It has been largely demonstrated that the activity of L-type Ca 2ϩ channels can be regulated by different types of kinases, such as protein kinase A (PKA) 1 (1,2) and protein kinase C (PKC) (3,4). These two kinases phosphorylate serine (Ser) and threonine (Thr) residues on the ␣and ␤-subunits of these channel proteins (5,6).…”

Functional expression of 5‐HT1c receptor cDNA in COS 7 cells and its influence on protein kinase C

“…It has been thought for a number of years that COS 7 cells expressed only the a isoform of PKC [26] and although there is recent evidence that < PKC may also be present [19], this isoform appears to have little affinity for phorbol esters [20] and therefore should not contribute to the current results. Both PDBu and DOG caused clear translocation of [3H]PDBu binding sites in COS 7 cells, although the effect of DOG (at a concentration maximal in other PKC response models [21,271 was much less than that of PDBu. This is entirely consistent with previous results which demonstrated that PKC a (predominant here in COS 7 cells) shows both a distinctively reduced binding affinity and potency of kinase activation with respect to short chain saturated diglycerides such as DOG but not phorbol esters [27].…”

“…In all of these experiments, translocation was observed after treatment with PDBu (300 nM) or DOG (200 PM) indicating that the cells would in principle have been capable of responding to any serotonin-elicited signal. Interestingly, DOG (200 PM) always caused much less translocation of [3H]PDBu binding sites than did PDBu (300 nM), even though these concentrations produce equivalent effects in a model of PKC-mediated facilitation of Ca2+ channels [21].…”