Table 1.

PTMs and mutation sites of kinase cascade regulating renal ion channel. Abbreviations: BP, Blood pressure; m, mice; h, human; auto, autophosphorylation; pRTA, proximal renal tubular acidosis.

Proteins	Upstream Regulator (Direct)	PTM Sites	PTM Modified Motif & Domain	PTM Effect	Effect on BP1	Ref	Mutation Sites	Clinical Significance *	Motif & Domain	Mutation Effect	Effect on BP	Ref
	The WNK Signaling
WNK4	SGK1 & PKA & PKC	p-S1169(m) = p-S1190(h)	COOH termini, RRXS motifs	inhibit ENaC	↓	[21,22]	S1169D		COOH termini	WNK4 gain of function; PHAII	↑	[23]
							S1169A		COOH termini	inhibit ENaC	↓	[21]
		p-S1196(m) = p-S1217(h)	COOH termini, RRXS motifs	WNK4 S332 autophosphorylation, reduces NCC inhibition	↑	[22,24]	S1196D		COOH termini	WNK4 gain of function	↑	[23]
	AKT & SGK1	p-S47(h)	NH2 termini, RRXS motifs	WNK4 S332 autophosphorylation, reduces NCC inhibition	↑	[25]
	PKA&PKC	p-S64(h)	NH2 termini, RRXS motifs	WNK4 S332 autophosphorylation	↑	[26]
	SGK1	p-S1800(m) = p-S1201(h)	COOH termini, RRXS motifs	activate WNK4	↑	[22]
	autophosphorylation	p-S332(m) = p-S335(h)	activation T-loop, kinase domain	activate WNK4	↑	[27]	S335A		activation T-loop, kinase domain	WNK4 loss of function	↓	[28]
							L322F		T-loop kinase domain	WNK4 gain of function	↑
							R1185C		CaM binding domain	WNK4 partially loss of function	↓	[29]
							D561A		acidic motif	prevent KLHL3 bind to WNK4	↑	[29,30,31]
							Q565E	Pathogenic
							E562K	Pathogenic
							D321A or D321K, K186D		T-loop kinase domain	WNK4 kinase dead	↓	[32]
	p38MAPK- MK pathway	p-S575(h)	near the acidic motif	activate WNK4	↑	[33]
WNK1	SGK1 & AKT	p-T58(m) = p-Thr60(h)	proline-rich domain (PRD)	inhibit ROMK	↑	[34,35]	T58A(m)		proline-rich domain (PRD)	WNK1 loss of function	↓	[34]
							K233M		subdomain I, kinase domain	WNK1 kinase dead	↓	[36]
	auto	p-S382(h)	activation T-loop, kinase domain	activate WNK4	↑	[17]	S382A		activation T-loop, kinase domain	WNK1 kinase dead	↓	[37]
							D368A		activation T-loop, kinase domain	WNK1 kinase dead	↓	[38]
							F316A		kinase domain	inhibit NCC	↓	[27]
							HQ/AA		coiled-coil domain, HQ motif	inhibit NCC	↓	[27]
							intron 1 479–667 deletion			WNK1 overexpression, PHAII	↑	[19,39]
WNK3	auto	p-S308, p-S304	activation T-loop, kinase domain	activate WNK3	↑	[33,40]
SPAK	WNK1, WNK3 & WNK4	T233	activation T-loop, kinase domain	activate SPAK	↑	[7]	T233E		activation T-loop, kinase domain	SPAK gain of function	↑	[41]
		S373, S387	COOH termini, S-motif	activate SPAK	↑	[7]
							T243A		activation T-loop, kinase domain	SPAK loss of function, Gitelman’s Syndrome	↓	[28,42]
OSR1	WNK1, WNK3 & WNK4	T185	activation T-loop, kinase domain	activate OSR1	↑	[7]	T185E		activation T-loop, kinase domain	OSR1 gain of function	↑	[41]
		S325, S339	COOH termini, S-motif	activate OSR1	↑	[7]			kidney-specific inactivation: KSP-OSR1-/-	OSR1 loss of function, Bartter’s Syndrome	↓	[43]
AKT	mTORC2	p-S473	hydrophobic motif	activate WNK1	↑	[44]
		p-T308	activation T-loop, kinase domain	activate WNK1	↑	[44]
SGK1	mTORC2	p-S422	hydrophobic motif	inhibit ROMK	↑	[17,45]	S422D		hydrophobic motif	SGK1 gain of function	↑	[24]
		p-T256	activation T-loop, kinase domain	activate WNK1	↑	[17,45]
							K127M		ATP-binding site in kinase domain	SGK1 kinase dead	↓	[24]
NEDD4.2	SGK1 & 14-3-3	p-S342, p-T367, p-S448	14-3-3 binding motifs	increase ENaC expression	↑	[46,47,48]
	AKT	p-S342, p-S428	between the WW domains	increase ENaC expression	↑	[47,49]
	PKA/PKC	p-S327, p-S221, p-T246	between the WW domains	inhibit Nedd4-2	↑	[50]
	NEDD4.2 WW domain	n/a	HECT domain, LPxY motif	increase ENaC expression	↑	[51]
CUL3							exon 9 deletion		NH2 termini	CUL3 loss of function, PHAIIE	↑	[52]
KLHL3	AKT, PKC & PKA	p-S433	kelch repeat region	increase WNK4 expression	↑	[53]	S433E		Kelch repeat region	KLHL3 loss of function	↑	[54]
							R528H	Pathogenic	Kelch repeat region	KLHL3 loss of function	↑	[55]
	Proximal Tubule (PT)
NHE3	SGK1	p-S663	RRxS motifs	increase NHE3 expression	↑	[56]	S663A		RRxS motifs	NHE3 loss of function	↓	[56]
	PKA	p-S555, p-S607	RRxS motifs	inhibit NHE3 expression	↓	[56]	S607A		RRxS motif	NHE3 gain of function	↑	[57]
NBC1	PKA	p-S1026	COOH termini	increase NBC1 expression	↑	[58]
		p-T49	NH2 termini	increase NBC1 expression	↑	[58]
							T485S or A799V or R881C			NBC1 gain of function	pRTA	[59,60]
	Thick Ascending Tubule (TAL)
NKCC2	SPAK & OSR1	p-S91, p-T95, p-T100, p-T105, p-T118, p-S120, p-S130	amino acid permease N-termini	NKCC2 activated	↑	[61,62,63]
NKCC1	SPAK & OSR1	p-T203, p-T207, p-T212, p-T230	amino acid permease N-termini	NKCC1 activated	↑	[64,65,66]
	Cortical Collecting Duct (CCD)
ROMK	WNK4	p-S44	inward rectifier potassium region	decrease ROMK expression	↓	[67,68]	S44D		inward rectifier potassium region	ROMK gain of function	↑	[69]
	SGK1 & PKA & PKC	p-S44	inward rectifier potassium region	increase ROMK expression	↑	[70]	S44A		inward rectifier potassium region	ROMK loss of function	↓	[69]
ENaC	NEDD4.2	u-βT613, u-γT623	PY motif	inhibit ENaC	↓	[71,72]			Truncation -SCNN1B: COOH termini SCNN1C: the PY motif, the Nedd4.2 binding site	ROMK gain of function Liddle’s Syndrome	↑	[6,73]
	Furin	cleaves α-subunit twice (after residue 181 and 204)	extracellular domain	activate ENaC	↑	[74,75,76]
		cleaves γ-subunit once (after residue 138)	extracellular domain	activate ENaC	↑	[74,75,76]
	prostasin	cleaves γ subunit at a defined polybasic (RKRK) tract	finger domain	activate ENaC	↑	[77]

↓ down-regulation; ↑ up-regulation. * The clinical significance of the genetic variants included in the table were referred from ClinVar database (https://www.ncbi.nlm.nih.gov/clinvar/, accessed on 27 August 2022). Only the variants that are documented as “pathogenic” are included.