Preprint Hypothesis Version 2 This version is not peer-reviewed

Hypothesis: Chemical Activity Regulates and Coordinates the Process Maintaining Glycerophospholipid Homeostasis in Mammalian Cells.

Version 1 : Received: 15 April 2019 / Approved: 19 April 2019 / Online: 19 April 2019 (07:38:21 CEST)
Version 2 : Received: 30 October 2019 / Approved: 31 October 2019 / Online: 31 October 2019 (04:39:47 CET)

How to cite: Somerharju, P.; Virtanen, J.A.; Hermansson, M. Hypothesis: Chemical Activity Regulates and Coordinates the Process Maintaining Glycerophospholipid Homeostasis in Mammalian Cells.. Preprints 2019, 2019040210 (doi: 10.20944/preprints201904.0210.v2). Somerharju, P.; Virtanen, J.A.; Hermansson, M. Hypothesis: Chemical Activity Regulates and Coordinates the Process Maintaining Glycerophospholipid Homeostasis in Mammalian Cells.. Preprints 2019, 2019040210 (doi: 10.20944/preprints201904.0210.v2).

Abstract

Mammalian cells maintain the complex glycerophospholipid (GPL) class compositions of their various membranes within close limits because this is essential to their well-being or viability. Surprisingly, however it is still not understood how those compositions are maintained except that GPL synthesis and degradation closely coordinated. Here, we hypothesize that abrupt changes in the chemical activity of the individual GPL classes coordinate the synthesis and degradation, as well other homeostatic processes. A previously proposed model proposed that in cellular membranes only a limited number of “allowed” or optimal GPL glass compositions exist because they are energetically more favorable than the other compositions, i.e. they represent local free energy minima (Somerharju et al. 2009). This model, however, could not satisfactorily explain how the optimal compositions are sensed by the key homeostatic enzymes i.e., the rate-limiting synthetizing enzymes and the degrading enzymes (i.e., homeostatic phospholipases). We now propose that when the mole fraction of a GPL class exceeds an optimal one, its chemical activity abruptly increases, which (i) increases its propensity to efflux from the membrane thus making it susceptible for hydrolysis by homeostatic phospholipases, (ii) increases its potency to inhibit its own biosynthesis via a feedback mechanism, (iii) enhances its conversion to another GPL class via a novel process termed “head group remodeling” or (iv) enhances its translocation to other subcellular membranes. Accordingly, abrupt changes in the chemical activity of the individual GPL classes is proposed to regulate and coordinate those four processes maintaining GPL class homeostasis in mammalian cells.

Subject Areas

regulation; membrane; glycerophospholipid; composition; chemical activity

Comments (1)

Comment 1
Received: 31 October 2019
Commenter: Pentti Somerharju
Commenter's Conflict of Interests: Author
Comment: We have modified the title and made minor changes to the text proper.
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