Cellular compartmentation of energy metabolism: creatine kinase microcompartments and recruitment of B-type creatine kinase to specific subcellular sites

Abstract

There is an increasing body of evidence for local circuits of ATP generation and consumption that are largely independent of global cellular ATP levels. These are mostly based on the formation of multiprotein(-lipid) complexes and diffusion limitations existing in cells at different levels of organization, e.g., due to the viscosity of the cytosolic medium, macromolecular crowding, multiple and bulky intracellular structures, or controlled permeability across membranes. Enzymes generating ATP or GTP are found associated with ATPases and GTPases enabling the direct fueling of these energy-dependent processes, and thereby implying that it is the local and not the global concentration of high-energy metabolites that is functionally relevant. A paradigm for such microcompartmentation is creatine kinase (CK). Cytosolic and mitochondrial isoforms of CK constitute a well established energy buffering and shuttling system whose functions are very much based on local association of CK isoforms with ATP-providing and ATP-consuming processes. Here we review current knowledge on the subcellular localization and direct protein and lipid interactions of CK isoforms, in particular about cytosolic brain-type CK (BCK) much less is known compared to muscle-type CK (MCK). We further present novel data on BCK, based on three different experimental approaches: (1) co-purification experiments, suggesting association of BCK with membrane structures such as synaptic vesicles and mitochondria, involving hydrophobic and electrostatic interactions, respectively; (2) yeast-two-hybrid analysis using cytosolic split-protein assays and the identifying membrane proteins VAMP2, VAMP3 and JWA as putative BCK interaction partners; and (3) phosphorylation experiments, showing that the cellular energy sensor AMP-activated protein kinase (AMPK) is able to phosphorylate BCK at serine 6 to trigger BCK localization at the ER, in close vicinity of the highly energy-demanding Ca(2+) ATPase pump. Thus, membrane localization of BCK seems to be an important and regulated feature for the fueling of membrane-located, ATP-dependent processes, stressing again the importance of local rather than global ATP concentrations.

International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine

“…Phosphagens are prevalent in all species and play an important role in maintaining energy availability [1, 2, 24, 25]. The primary metabolic role of creatine is to combine with a phosphoryl group (Pi) to form PCr through the enzymatic reaction of creatine kinase (CK).…”

“…Wallimann and colleagues [26–28] suggested that the pleiotropic effects of Cr are mostly related to the functions of CK and PCr (i.e., CK/PCr system). As adenosine triphosphate (ATP) is degraded into adenosine diphosphate (ADP) and Pi to provide free energy for metabolic activity, the free energy released from the hydrolysis of PCr into Cr + Pi can be used as a buffer to resynthesize ATP [24, 25]. This helps maintain ATP availability particularly during maximal effort anaerobic sprint-type exercise.…”

“…2). The CK/PCr energy shuttle connects sites of ATP production (glycolysis and mitochondrial oxidative phosphorylation) with subcellular sites of ATP utilization (ATPases) [24, 25, 27]. In this regard, creatine enters the cytosol through a CRTR [16, 29–31].…”

Assessing tissue metabolism by phosphorous-31 magnetic resonance spectroscopy and imaging: a methodology review

“…Besides oxidative phosphorylation, creatine kinase (CK) is also a key player in maintaining cellular energy homeostasis in many metabolically demanding tissues including muscle and brain (57). CK uses creatine (Cr) for reversible phosphoryl transfer between ATP and PCr in the following reaction:…”

Creatine: a miserable life without it

“…Using sophisticated membrane and vesicle isolation procedures and yeast two-hybrid analysis suited to identify membrane proteins as interaction partners, Schlattner et al (2016) identified a number of membrane proteins of the brain associated with brain-type cytosolic BB-CK. These novel micro-compartments of BB-CK with, for example, VAMP2 proteins and JWA, shed new light on synaptic functions dependent on BB-CK-mediated energy provision.…”